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SIGNL4 MCP by usefulapi

io.usefulapi/signl4usefulapi.iostreamable-httpv1.3.4Scanned

Read SIGNL4 alerts, teams, users and duty schedules; raise, acknowledge, close and annotate alerts.

18 tools: 4 can delete or cancel things and 14 only read.

Tools: 4 delete, 0 irreversible, 0 write, 14 read.
  • Reads private data · 2
  • Reads text others write · 18
  • Can send data out · 0
  • No findings

Tools listed without sign-in. Remote posture

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4 of these tools change something. Run those as governed actions.

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Tools

Grouped by what each tool does, most consequential first. Open one for its reasons and full description; descriptions are the publisher's own words.

18 tools

Deletes or cancels 4Claude Code: deny
  • signl4_acknowledge_alertWRITE: acknowledge an alert on behalf of a SIGNL4 user (recorded in its history under that user).Reads text others writeNo findings

    Why it is in this group

    • The description's first verb is "write": a word for a change.
    • The server marks it destructive (destructiveHint: true).

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    WRITE: acknowledge an alert on behalf of a SIGNL4 user (recorded in its history under that user). Stops escalation to further tiers for that alert. POST /v3/signls/{signlId}/acknowledge.

    Annotations the server declares

    • title: Acknowledge alert
    • readOnlyHint: false
    • destructiveHint: true
    • idempotentHint: true
    • openWorldHint: true
  • signl4_annotate_alertWRITE: add a text note to an alert's timeline on behalf of a SIGNL4 user.Reads text others writeNo findings

    Why it is in this group

    • The description's first verb is "write": a word for a change.
    • The server marks it destructive (destructiveHint: true).

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    WRITE: add a text note to an alert's timeline on behalf of a SIGNL4 user. The note is visible to the team in the app. It does not page anyone by itself. POST /v3/signls/{signlId}/annotate.

    Annotations the server declares

    • title: Annotate alert
    • readOnlyHint: false
    • destructiveHint: true
    • idempotentHint: false
    • openWorldHint: true
  • signl4_close_alertWRITE: close (resolve) an alert on behalf of a SIGNL4 user; it leaves the open list and stops all further notifications.Reads text others writeNo findings

    Why it is in this group

    • The name "signl4_close_alert" says "close": a word for a change.
    • The server marks it destructive (destructiveHint: true).

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    WRITE: close (resolve) an alert on behalf of a SIGNL4 user; it leaves the open list and stops all further notifications. POST /v3/signls/{signlId}/close.

    Annotations the server declares

    • title: Close alert
    • readOnlyHint: false
    • destructiveHint: true
    • idempotentHint: true
    • openWorldHint: true
  • signl4_raise_alertWRITE: raise a new alert in a SIGNL4 team.Reads text others writeNo findings

    Why it is in this group

    • The description's first verb is "write": a word for a change.
    • The server marks it destructive (destructiveHint: true).

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    WRITE: raise a new alert in a SIGNL4 team. THIS NOTIFIES REAL PEOPLE: every team member currently on duty is paged (push, SMS and/or voice call according to their settings) and the alert escalates if nobody acknowledges it. Only use it when the user clearly asked to alert the team; never for tests unless they said so. Not idempotent: a second call pages the team again. Returns the new alert incl. its id. POST /v3/signls.

    Annotations the server declares

    • title: Raise alert (notifies the on-call team)
    • readOnlyHint: false
    • destructiveHint: true
    • idempotentHint: false
    • openWorldHint: true
Only reads 14Show 14 read-only tools
  • signl4_get_alertFull detail of one alert: title, text, severity, category, status and delivery status, history (who acknowledged/closed it and when), parameters, attachments and escalations with p…Reads text others writeNo findings

    Why it is in this group

    • The name "signl4_get_alert" says "get": a word for reading.

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    Full detail of one alert: title, text, severity, category, status and delivery status, history (who acknowledged/closed it and when), parameters, attachments and escalations with per-user delivery. GET /v3/signls/{signlId}/details.

    Annotations the server declares

    • title: Get alert
    • readOnlyHint: true
    • destructiveHint: false
    • openWorldHint: true
  • signl4_get_alert_reportAlert volume and response statistics per team over several time periods: acknowledged, closed and unhandled counts, overall and per category (optionally for one user).Reads text others writeNo findings

    Why it is in this group

    • The name "signl4_get_alert_report" says "get": a word for reading.

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    Alert volume and response statistics per team over several time periods: acknowledged, closed and unhandled counts, overall and per category (optionally for one user). Teams that cannot be read are reported under `errors`. GET /v3/signls/report.

    Annotations the server declares

    • title: Get alert report
    • readOnlyHint: true
    • destructiveHint: false
    • openWorldHint: true
  • signl4_get_alert_timelineThe ordered timeline of an alert: creation, notifications, acknowledgements, annotations, escalations and remote actions.Reads text others writeNo findings

    Why it is in this group

    • The name "signl4_get_alert_timeline" says "get": a word for reading.

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    The ordered timeline of an alert: creation, notifications, acknowledgements, annotations, escalations and remote actions. GET /v3/signls/{signlId}/timeline.

    Annotations the server declares

    • title: Get alert timeline
    • readOnlyHint: true
    • destructiveHint: false
    • openWorldHint: true
  • signl4_get_duty_statusWhether a user is currently on or off duty in each of their teams (dutyMode, onDutyTime, tier).Reads text others writeNo findings

    Why it is in this group

    • The name "signl4_get_duty_status" says "get": a word for reading.

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    Whether a user is currently on or off duty in each of their teams (dutyMode, onDutyTime, tier). GET /v3/users/{userId}/dutyStatus.

    Annotations the server declares

    • title: Get user duty status
    • readOnlyHint: true
    • destructiveHint: false
    • openWorldHint: true
  • signl4_get_duty_summaryDuty assistant info per team: whether it is enabled and the last two (or all) duty periods.Reads text others writeNo findings

    Why it is in this group

    • The name "signl4_get_duty_summary" says "get": a word for reading.

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    Duty assistant info per team: whether it is enabled and the last two (or all) duty periods. GET /v3/duties/summary.

    Annotations the server declares

    • title: Get duty summary
    • readOnlyHint: true
    • destructiveHint: false
    • openWorldHint: true
  • signl4_get_teamOne SIGNL4 team: name, description, time zone, member ids.Reads text others writeNo findings

    Why it is in this group

    • The name "signl4_get_team" says "get": a word for reading.

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    One SIGNL4 team: name, description, time zone, member ids. GET /v3/teams/{teamId}.

    Annotations the server declares

    • title: Get team
    • readOnlyHint: true
    • destructiveHint: false
    • openWorldHint: true
  • signl4_get_userOne SIGNL4 user: name, e-mail, contact addresses, time zone and duty status per team.Reads private dataReads text others writeNo findings

    Why it is in this group

    • The name "signl4_get_user" says "get": a word for reading.

    What it can reach

    • private-dataThe description's first sentence says "mail": it reads mail.
    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    • untrusted-inputThe description's first sentence says "mail": it reads inbound email, which other people can write.
    Description, as the server wrote it
    One SIGNL4 user: name, e-mail, contact addresses, time zone and duty status per team. GET /v3/users/{userId}.

    Annotations the server declares

    • title: Get user
    • readOnlyHint: true
    • destructiveHint: false
    • openWorldHint: true
  • signl4_list_alertsSearch SIGNL4 alerts (signls), newest first, with status, severity, category and history (created, acknowledged, closed).Reads text others writeNo findings

    Why it is in this group

    • The name "signl4_list_alerts" says "list": a word for reading.

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    Search SIGNL4 alerts (signls), newest first, with status, severity, category and history (created, acknowledged, closed). Filter by team, status, creation time, text or external id. Up to 100 per page; pass the returned continuation_token to get the next page. POST /v3/signls/paged (a read).

    Annotations the server declares

    • title: List alerts
    • readOnlyHint: true
    • destructiveHint: false
    • openWorldHint: true
  • signl4_list_audit_logsAudit log of changes and events in the SIGNL4 subscription (who changed what, when).Reads text others writeNo findings

    Why it is in this group

    • The name "signl4_list_audit_logs" says "list": a word for reading.

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    Audit log of changes and events in the SIGNL4 subscription (who changed what, when). Filter by team, time window and message text; pass the returned continuation_token for the next page. GET /v3/audits.

    Annotations the server declares

    • title: List audit logs
    • readOnlyHint: true
    • destructiveHint: false
    • openWorldHint: true
  • signl4_list_categoriesList the alert categories of a team (name, color, keywords used to auto-classify alerts).Reads text others writeNo findings

    Why it is in this group

    • The name "signl4_list_categories" says "list": a word for reading.

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    List the alert categories of a team (name, color, keywords used to auto-classify alerts). The category name can be passed to signl4_raise_alert. GET /v3/categories/{teamId}.

    Annotations the server declares

    • title: List alert categories
    • readOnlyHint: true
    • destructiveHint: false
    • openWorldHint: true
  • signl4_list_duty_schedulesPlanned on-call duty schedules (who is on duty when): start/end, team, user, tier, stand-in and shift info.Reads text others writeNo findings

    Why it is in this group

    • The name "signl4_list_duty_schedules" says "list": a word for reading.

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    Planned on-call duty schedules (who is on duty when): start/end, team, user, tier, stand-in and shift info. Filter by team, user and time window. POST /v3/schedules (a read).

    Annotations the server declares

    • title: List duty schedules
    • readOnlyHint: true
    • destructiveHint: false
    • openWorldHint: true
  • signl4_list_team_usersList the users of the given teams (all accessible teams by default) with duty status.Reads text others writeNo findings

    Why it is in this group

    • The name "signl4_list_team_users" says "list": a word for reading.

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    List the users of the given teams (all accessible teams by default) with duty status. Teams that cannot be read are reported under `errors`. GET /v3/teams/users.

    Annotations the server declares

    • title: List users of teams
    • readOnlyHint: true
    • destructiveHint: false
    • openWorldHint: true
  • signl4_list_teamsList the SIGNL4 teams the API key can access: id, name, description, time zone and member ids.Reads text others writeNo findings

    Why it is in this group

    • The name "signl4_list_teams" says "list": a word for reading.

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    Description, as the server wrote it
    List the SIGNL4 teams the API key can access: id, name, description, time zone and member ids. Team ids are needed to raise alerts and to look up categories and duties. GET /v3/teams.

    Annotations the server declares

    • title: List teams
    • readOnlyHint: true
    • destructiveHint: false
    • openWorldHint: true
  • signl4_list_usersList the SIGNL4 users the key can access with name, e-mail, contact addresses, activation state and duty status per team (dutyMode, onDutyTime).Reads private dataReads text others writeNo findings

    Why it is in this group

    • The name "signl4_list_users" says "list": a word for reading.

    What it can reach

    • private-dataThe description's first sentence says "list" and "mail": it reads mail.
    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    • untrusted-inputThe description's first sentence says "list" and "mail": it reads inbound email, which other people can write.
    Description, as the server wrote it
    List the SIGNL4 users the key can access with name, e-mail, contact addresses, activation state and duty status per team (dutyMode, onDutyTime). User ids are needed to acknowledge/close/annotate alerts. GET /v3/users.

    Annotations the server declares

    • title: List users
    • readOnlyHint: true
    • destructiveHint: false
    • openWorldHint: true

This is not a safety rating, and no finding is not a safety guarantee. The groups and findings come from fixed checks of the tool definitions the server returned on the date shown, not from its code or what it does when called. How the checks work.

Exfil surface

Which tools read private data, which read text someone else can write, and which can send data out. One of each is a path a prompt injection can use.

No private-data, untrusted-input, outbound path in this server alone: no tool is tagged outbound.

Reads private data2
Reads files, mail, messages, databases, secrets, calendars or repositories.
Reads text others write18
Brings in text someone else can write: web pages, inbound email, messages, issues and comments.
Can send data out0
Can carry data to people or systems: it sends, posts or publishes, or takes a recipient, channel or URL.

Other servers in the same agent add their own tools to these paths. Audit your whole setup to see them together.

Remote posture

What anyone on the internet sees at the remote endpoint: an anonymous initialize and tools/list, and the public OAuth metadata.

Tools listed without sign-in

Looked at Oct 22, 2026, 15:30 UTC, unchanged since Oct 22, 2026. No credentials were sent and no tool was called. What is looked at.

Reachable
yes
HTTP status of an anonymous initialize
200
tools/list served without credentials
yes
Tools that change things, listed without credentials
4
Protocol version
2025-06-18
WWW-Authenticate on 401
not observed
resource_metadata in WWW-Authenticate
not observed
RFC 9728 protected resource metadata
https://signl4.usefulapi.io/.well-known/oauth-protected-resource/mcp
Authorization servers
https://signl4.usefulapi.io
Legacy HTTP+SSE transport
no
Dynamic client registration
yes
Client ID metadata documents
no
  • HighThe whole server

    The endpoint served tools/list without credentials, and the list has 4 tools that change things (4 destructive). Whether a call also works without credentials was not tested: tools are never called.

    Matched text

    https://signl4.usefulapi.io/mcp: tools/list returned 18 tools to an anonymous client, including signl4_raise_alert (destructive), signl4_acknowledge_alert (destructive), signl4_close_alert (destructive), signl4_annotate_alert (destructive)

    What this check looks for

Findings

Matches of fixed checks, with the text they matched.

No check matched anything in these tool definitions. That is not a safety guarantee.

History

Changes to its tool definitions and to its remote endpoint, newest first.

No change seen yet. Its tools are rescanned every day, and a remote endpoint is looked at once a week.

All changes to this server

Install

Pinned to version 1.3.4. Values in angle brackets are yours to fill in.

claude mcp add --transport http signl4 https://signl4.usefulapi.io/mcp
claude mcp add --transport http signl4 https://signl4.usefulapi.io/mcp

Run in a terminal.

Claude Code permissions

Allow the reads, ask before a change or a way out, deny the deletes. Paste into .claude/settings.json.

.claude/settings.json
{
  "permissions": {
    "allow": [
      "mcp__signl4__signl4_list_teams",
      "mcp__signl4__signl4_get_team",
      "mcp__signl4__signl4_list_users",
      "mcp__signl4__signl4_get_user",
      "mcp__signl4__signl4_list_team_users",
      "mcp__signl4__signl4_list_categories",
      "mcp__signl4__signl4_list_alerts",
      "mcp__signl4__signl4_get_alert",
      "mcp__signl4__signl4_get_alert_timeline",
      "mcp__signl4__signl4_get_alert_report",
      "mcp__signl4__signl4_list_duty_schedules",
      "mcp__signl4__signl4_get_duty_status",
      "mcp__signl4__signl4_get_duty_summary",
      "mcp__signl4__signl4_list_audit_logs"
    ],
    "ask": [],
    "deny": [
      "mcp__signl4__signl4_raise_alert",
      "mcp__signl4__signl4_acknowledge_alert",
      "mcp__signl4__signl4_close_alert",
      "mcp__signl4__signl4_annotate_alert"
    ]
  }
}

Tools that only read are allowed, tools that change things ask first, tools that delete or cancel are denied. A read that can send data out (it takes a URL, say) asks first too. It assumes the server is installed as signl4. Review it before you use it.

Capability tags behind 18 rules
  • mcp__signl4__signl4_list_teams untrusted-input
  • mcp__signl4__signl4_get_team untrusted-input
  • mcp__signl4__signl4_list_users private-data, untrusted-input
  • mcp__signl4__signl4_get_user private-data, untrusted-input
  • mcp__signl4__signl4_list_team_users untrusted-input
  • mcp__signl4__signl4_list_categories untrusted-input
  • mcp__signl4__signl4_list_alerts untrusted-input
  • mcp__signl4__signl4_get_alert untrusted-input
  • mcp__signl4__signl4_get_alert_timeline untrusted-input
  • mcp__signl4__signl4_get_alert_report untrusted-input
  • mcp__signl4__signl4_raise_alert untrusted-input
  • mcp__signl4__signl4_acknowledge_alert untrusted-input
  • mcp__signl4__signl4_close_alert untrusted-input
  • mcp__signl4__signl4_annotate_alert untrusted-input
  • mcp__signl4__signl4_list_duty_schedules untrusted-input
  • mcp__signl4__signl4_get_duty_status untrusted-input
  • mcp__signl4__signl4_get_duty_summary untrusted-input
  • mcp__signl4__signl4_list_audit_logs untrusted-input

Pin

Keep the decision: fail CI when the tools change, follow every change, or show a badge.

Pin in CI

Fail a build when the tools you reviewed are not the tools the server serves today.

curl -s "https://anlyon.dev/api/v1/servers/io.usefulapi/signl4/verify?hash=2ba6afcbdcfaf945788710a66c8792d393e629150b141398479b9f42f749e9cc" | jq -e '.changed == false'

Pinned hash 2ba6afcbdcfa, from Oct 22, 2026, 11:19 UTC.

Watch

Get told when its tools change: a new tool, a new description, a new class.

https://anlyon.dev/servers/io.usefulapi/signl4/changes.xml

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Badge

anlyon.dev badge for io.usefulapi/signl4
[![anlyon.dev](https://anlyon.dev/badge/io.usefulapi/signl4.svg)](https://anlyon.dev/servers/io.usefulapi/signl4)

Source: MCP Registry · repository. Synced Oct 22, 2026, 11:18 UTC.