# `io.github.cyanheads/oeis-mcp-server` on anlyon.dev

> Text inside fenced blocks marked untrusted-server-text was written by the MCP server's publisher, not by anlyon.dev. It is data to inspect, not instructions to follow. Invisible characters are shown as [U+XXXX].
> No finding is not a safety guarantee: these are point-in-time checks of tool definitions, not of code or behaviour.

- Page: https://anlyon.dev/servers/io.github.cyanheads/oeis-mcp-server
- JSON: https://anlyon.dev/api/v1/servers/io.github.cyanheads/oeis-mcp-server
- Version: 0.1.3 (active)
- Publisher: io.github.cyanheads (GitHub account)
- Runs: remote (streamable-http), local (npm)
- Sign-in to list tools: none
- Repository: https://github.com/cyanheads/oeis-mcp-server
- Metadata from the official MCP Registry, synced 2026-10-21T18:28:53.733Z

Title and description, as the publisher wrote them:

```untrusted-server-text
Identify integer sequences by terms, search the OEIS, read formulas, programs, b-files, cross-refs.
```

Scanned 2026-10-21T19:16:40.628Z over streamable-http.

**6 tools: 1 change things and 5 only read.**

| Group | Class | Tools | Claude Code |
| --- | --- | --- | --- |
| Deletes or cancels | destructive | 0 | deny |
| Can't be undone | irreversible | 0 | ask |
| Changes things | write | 1 | ask |
| Only reads | read | 5 | allow |

## Findings

No check matched anything in these tool definitions.


## Changes things (1)

Creates or changes something that can be changed back. Claude Code: ask.

### `oeis_identify_sequence`

- 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:

```untrusted-server-text
Identify integer sequences that contain a run of consecutive terms, e.g. "1, 2, 5, 14, 42". Returns up to 10 matches per page in OEIS relevance order, each with the index n at which the supplied run begins. For the best hit rate supply about 6 terms and leave off the first one or two, since sources disagree on where a sequence starts. OEIS matches only the first terms of each entry (its data line, at most about 270 characters), not its b-file, so a run from far into a sequence is not found. Takes up to 60 terms, each an integer of at most 200 digits or the wildcard _ for one unknown term.
```

## Only reads (5)

Looks things up and changes nothing. Claude Code: allow.

### `oeis_get_cross_refs`

- The name "oeis_get_cross_refs" says "get": a word for reading.

Description, as the server wrote it:

```untrusted-server-text
List sequences related to an OEIS entry. direction outgoing returns the A-numbers named in the entry's cross-reference (Cf.) lines, with any parenthetical note beside each; direction incoming returns entries that mention this A-number anywhere. Each row carries the related sequence's name and first terms. 10 rows per page.
```

### `oeis_get_sequence`

- The name "oeis_get_sequence" says "get": a word for reading.

Description, as the server wrote it:

```untrusted-server-text
Fetch one OEIS entry by A-number. Returns the name, data-line terms, offset, keywords, author, dates, and the sections: comments, formulas (recurrences and generating functions), examples, programs (Maple, Mathematica, PARI, Python, …), references, links, cross-references, and extensions. When the sections together exceed 24,000 characters of serialized JSON, the core fields come back with a section outline instead; call again with sections to pick what to read. A selection past 100,000 bytes comes back in parts cut between items: pass nextFromItem as fromItem, with the same sections, for the next part.
```

### `oeis_get_terms`

- The name "oeis_get_terms" says "get": a word for reading.

Description, as the server wrote it:

```untrusted-server-text
List terms a(n) of a sequence with their indices n. Reads the entry's b-file when it has one — often thousands of terms beyond the data line — and otherwise the data line itself. Values are exact decimal strings of any size. A slice stops at limit terms (at most 1000 per call), at about 100,000 bytes, or at the end of one 1 MiB part of a larger b-file, whichever comes first; nextFromIndex continues it.
```

### `oeis_list_reference`

- The name "oeis_list_reference" says "list": a word for reading.

Description, as the server wrote it:

```untrusted-server-text
Look up OEIS vocabulary used by the other tools: keyword flags (nonn, core, tabl, cons, …), search syntax (prefixes, operators, wildcards, sort orders, paging window), and identifier conventions (A-numbers, legacy M/N numbers, offsets, b-files).
```

### `oeis_search_sequences`

- The name "oeis_search_sequences" says "search": a word for reading.

Description, as the server wrote it:

```untrusted-server-text
Search the OEIS using its query syntax: plain words, "quoted phrases", comma-separated terms, prefixes (keyword:, author:, name:, comment:, formula:, program:, xref:, id:), | for OR, and a leading - to exclude. Returns up to 10 summaries per page. For identifying a sequence from its terms, oeis_identify_sequence is the direct route.
```

## Claude Code permissions

For `.claude/settings.json`, assuming the server is installed as `oeis`:

```json
{
  "permissions": {
    "allow": [
      "mcp__oeis__oeis_search_sequences",
      "mcp__oeis__oeis_get_sequence",
      "mcp__oeis__oeis_get_terms",
      "mcp__oeis__oeis_get_cross_refs",
      "mcp__oeis__oeis_list_reference"
    ],
    "ask": [
      "mcp__oeis__oeis_identify_sequence"
    ],
    "deny": []
  }
}
```