Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations only signal that this is neither read-only nor destructive, but the description goes beyond them by disclosing that the new secret is returned once, that the old secret will fail with 401 invalid_api_key, that identity and credits are unchanged, and that the Bearer header is preferred. It also includes the operational caveat about not editing ops files. No contradiction with the annotations exists.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is six short sentences, each carrying a distinct piece of information: the operation, identity/credit preservation, one-time secret output, old-secret failure behavior, auth preference, and an ops limitation. It is front-loaded with the primary verb and resource and contains no filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a no-parameter, no-output-schema tool, the description covers purpose, side effects, output, error behavior, and authentication well. The main gaps are the absence of explicit routing guidance relative to issue_key/revoke_key and the unexplained connection to the feed/digest/atom terms present in the tool title.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool has zero schema parameters, so the baseline is 4; the description still adds meaning by explaining how the 'presented secret' is supplied via Authorization: Bearer and that X-API-Key is merely an alias. This is effective parameter-level guidance even though the input schema is empty.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a concrete action, 'Replace the presented secret (POST /keys/rotate)', and immediately clarifies that the same id/caller_id and credits are preserved. This makes the operation unambiguous and distinguishes it from siblings such as issue_key or revoke_key without needing to inspect their schemas. The slightly noisy title is outweighed by the clear, specific body text.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description clearly establishes the context: use this tool to rotate the presented secret while keeping identity and credits intact, and it adds operational guidance about authentication ('Prefer Authorization: Bearer; X-API-Key is an alias only') and an explicit boundary ('No ops file-edit'). It does not explicitly name sibling alternatives or provide a 'use this instead of X when...' statement, so the alternative routing is implied rather than fully explicit.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.