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

Annotations only declare readOnlyHint=true, so the description carries the rest: it discloses that the key hash and full secret are never returned, and that a JWT-authenticated call fails with a specific 400 code. That is meaningful behavioral context beyond the annotation, though response shape/pagination detail is absent.

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?

Two short paragraphs, front-loaded with the purpose and return fields, followed by the access/auth caveat. The ACCESS note is slightly verbose but every sentence conveys actionable routing information.

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?

With no output schema, the description compensates by enumerating returned fields, and it covers the auth model, a specific error condition, and the setup path for Claude Code. Nothing needed to call this zero-parameter tool correctly is missing.

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 takes zero parameters, so the baseline is 4. The description usefully lists the fields present in the returned object (id, name, key_prefix, environment, scopes, last_used_at, revoked_at, created_at) in the absence of an output schema.

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?

States a specific verb+resource ('Get the calling API key's own redacted metadata') and enumerates the exact returned fields, making it clearly distinguishable from siblings like list_api_keys and get_api_key_usage. The scope is narrowed to self-inspection of the authenticated key.

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?

Explains the selection context ('for agent self-inspection') and, unusually, the auth precondition plus the failure mode ('a JWT session has no single-key context (returns 400 api_key_required)'), and warns that 'start_login does NOT open this tool'. It doesn't explicitly name list_api_keys as the alternative for enumerating other keys, so it falls short of a 5.

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