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I Bond Rate MCP

io.github.theluckystrike/i-bond-rate-mcptheluckystrikestreamable-httpv1.0.0Scanned

Current I bond rate, what your I bond earns by issue month, and value estimates from TreasuryDirect.

5 tools: 2 change things and 3 only read.

Tools: 0 delete, 0 irreversible, 2 write, 3 read.
  • Reads private data · 0
  • Reads text others write · 2
  • Can send data out · 0
  • 1 finding

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

Declare what an action changes, and Anlyon puts it under a shared limit, binds every approval to the exact request, and grades the outcome. It works on any HTTPS API you can describe as an action.

Anlyon does not run, proxy or govern this MCP server. A tool your own code calls directly is not routed through Anlyon and is not governed by it.

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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.

5 tools

Changes things 2Claude Code: ask
  • calculate_i_bond_composite_rateApply the Treasury formula fixed + 2 x semiannual inflation + fixed x semiannual inflation, rounded to 0.01 percent with a floor of zero.1 finding

    Why it is in this group

    • The description's first verb is "apply": a word for a change.
    • The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.

    Findings

    • Warn

      The server marks "calculate_i_bond_composite_rate" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

      Matched text

      annotations: {"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}; The description's first verb is "apply": a word for a change.

      What this check looks for
    Description, as the server wrote it
    Apply the Treasury formula fixed + 2 x semiannual inflation + fixed x semiannual inflation, rounded to 0.01 percent with a floor of zero. Use it for rate predictions.

    Annotations the server declares

    • title: Composite rate formula
    • readOnlyHint: true
    • destructiveHint: false
    • idempotentHint: true
    • openWorldHint: false
  • estimate_i_bond_valueEstimate what I bonds are worth for an issue month and purchase amount at the start of a month: value with all interest and the redemption value after the 3-month penalty for bonds…No findings

    Why it is in this group

    • Nothing in its name or description says what it does, so it is counted as a write.
    • The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.
    Description, as the server wrote it
    Estimate what I bonds are worth for an issue month and purchase amount at the start of a month: value with all interest and the redemption value after the 3-month penalty for bonds under 5 years. Uses semiannual compounding per $25 with the TreasuryDirect rates. An estimate; Treasury values can differ by cents.

    Annotations the server declares

    • title: I bond value estimate
    • readOnlyHint: true
    • destructiveHint: false
    • idempotentHint: true
    • openWorldHint: false
Only reads 3Show 3 read-only tools
  • get_current_i_bond_rateCurrent Series I savings bond composite rate, fixed rate and semiannual inflation rate for new purchases, read at call time from the TreasuryDirect "I bonds interest rates" page wi…Reads text others writeNo findings

    Why it is in this group

    • The name "get_current_i_bond_rate" 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
    Current Series I savings bond composite rate, fixed rate and semiannual inflation rate for new purchases, read at call time from the TreasuryDirect "I bonds interest rates" page with the built-in rate chart as fallback. November 2026 to April 2027: 5.51 percent with a 1.40 percent fixed rate. Also returns the next announcement date and the $10,000 limit, 12-month hold and 3-month penalty rules.

    Annotations the server declares

    • title: Current I bond rate
    • readOnlyHint: true
    • destructiveHint: false
    • idempotentHint: true
    • openWorldHint: true
  • get_i_bond_rate_for_issue_dateFor an I bond bought in a given month: its fixed rate, the composite rate it earns in the current (or given) 6-month period, the months its rate changes, whether it can be cashed a…Reads text others writeNo findings

    Why it is in this group

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

    What it can reach

    • untrusted-inputThe name "get_i_bond_rate_for_issue_date" says "get" and "issue": it reads issues, which other people can write.
    • untrusted-inputThe description's first sentence says "issue": it reads issues, which other people can write.
    Description, as the server wrote it
    For an I bond bought in a given month: its fixed rate, the composite rate it earns in the current (or given) 6-month period, the months its rate changes, whether it can be cashed and the penalty, and every rate period since issue. Computed from the TreasuryDirect rate chart effective November 1, 2026.

    Annotations the server declares

    • title: I bond rate by issue date
    • readOnlyHint: true
    • destructiveHint: false
    • idempotentHint: true
    • openWorldHint: false
  • get_i_bond_rate_historyFixed rate for new bonds, semiannual inflation rate and composite rate for every May and November announcement since September 1998, newest first, from the TreasuryDirect rate char…No findings

    Why it is in this group

    • The name "get_i_bond_rate_history" says "get": a word for reading.
    Description, as the server wrote it
    Fixed rate for new bonds, semiannual inflation rate and composite rate for every May and November announcement since September 1998, newest first, from the TreasuryDirect rate chart.

    Annotations the server declares

    • title: I bond rate history
    • readOnlyHint: true
    • destructiveHint: false
    • idempotentHint: true
    • openWorldHint: false

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 private-data or outbound.

Reads private data0
Reads files, mail, messages, databases, secrets, calendars or repositories.
Reads text others write2
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.

Findings

Matches of fixed checks, with the text they matched.

1 warn
  • Warncalculate_i_bond_composite_rate

    The server marks "calculate_i_bond_composite_rate" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

    Matched text

    annotations: {"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}; The description's first verb is "apply": a word for a change.

    What this check looks for

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 1.0.0. Values in angle brackets are yours to fill in.

claude mcp add --transport http i-bond-rate https://i-bond-rate-mcp.lipmichal.workers.dev/mcp
claude mcp add --transport http i-bond-rate https://i-bond-rate-mcp.lipmichal.workers.dev/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__i-bond-rate__get_current_i_bond_rate",
      "mcp__i-bond-rate__get_i_bond_rate_for_issue_date",
      "mcp__i-bond-rate__get_i_bond_rate_history"
    ],
    "ask": [
      "mcp__i-bond-rate__estimate_i_bond_value",
      "mcp__i-bond-rate__calculate_i_bond_composite_rate"
    ],
    "deny": []
  }
}

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 i-bond-rate. Review it before you use it.

Capability tags behind 2 rules
  • mcp__i-bond-rate__get_current_i_bond_rate untrusted-input
  • mcp__i-bond-rate__get_i_bond_rate_for_issue_date 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.github.theluckystrike/i-bond-rate-mcp/verify?hash=02282baf86662ef08a996f15f71ee54fc6bdf4c37020f27a7109bcd7f6be14d1" | jq -e '.changed == false'

Pinned hash 02282baf8666, from Nov 5, 2026, 14:18 UTC.

Watch

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

https://anlyon.dev/servers/io.github.theluckystrike/i-bond-rate-mcp/changes.xml

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Source: MCP Registry · repository. Synced Nov 5, 2026, 14:18 UTC.