fix: add tool annotations to server-fetch

[Chelebii]

This PR adds missing tool annotations (readOnlyHint, idempotentHint, openWorldHint) to the fetch tool in @modelcontextprotocol/server-fetch. This follows the pattern in other reference servers and provides better metadata for MCP clients. Fixes #3572.

[cliffhall]

@claude review

[claude]

Claude finished @cliffhall's task in 1m 36s —— View job

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PR Review: fix: add tool annotations to server-fetch

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Summary

This is a clean, focused PR that adds ToolAnnotations to the fetch tool in server-fetch. The change is minimal (7 lines added, 0 deleted) and follows the established pattern in the codebase. Here's a detailed look:

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What changed

src/fetch/src/mcp_server_fetch/server.py — two additions:

1. Import of ToolAnnotations from mcp.types (line 17)
2. Annotations block on the fetch tool definition (lines 207–212):

annotations=ToolAnnotations(
    readOnlyHint=True,
    destructiveHint=False,
    idempotentHint=True,
    openWorldHint=True,
),

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Annotation value review

Annotation	Value	Assessment
readOnlyHint	True	✅ Correct — fetch only reads web content, modifies no state
destructiveHint	False	✅ Correct — not destructive
idempotentHint	True	✅ Acceptable — no side effects; consistent with sequentialthinking pattern
openWorldHint	True	✅ Correct — makes real network calls to external URLs

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Minor observations

destructiveHint=False is technically redundant when readOnlyHint=True. Per the MCP spec, destructiveHint "only applies to tools that modify their environment; it has no meaning for read-only tools." That said, the sequentialthinking server (src/sequentialthinking/index.ts:96) uses the same explicit pattern, so this is consistent with project style — not a blocker.

idempotentHint=True with openWorldHint=True — these aren't contradictory. idempotentHint signals "no additional side effects from repeated calls", not "always returns the same result." Since fetch performs no state mutations, this is accurate.

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Code quality

• Import placement is correct — ToolAnnotations is added in the existing mcp.types import block in alphabetical order.
• Pattern matches how the Python SDK is already used elsewhere in the project.
• No tests are needed — this is pure metadata visible to MCP clients only.

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Verdict

LGTM. The change is correct, minimal, and consistent with the existing codebase patterns. No functional or security concerns.

[LuuOW]

Technical audit: Verified MCP server implementation for consistency with current SDK patterns.