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

Discloses crucial runtime behavior beyond annotations: the new whi_… key is returned only once, the old key subsequently fails with 401 invalid_api_key, and id/caller_id and credits are preserved. This is rich, non-obvious context an agent needs.

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?

Three dense sentences, each earning its place: what happens, what is returned, and how to authenticate. Front-loaded with the core operation and 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?

Despite no output schema, the description covers the response (new key returned once), the failure mode (401), side effects (old key invalid), and invariants (same id/credits). Nothing essential is missing for an agent to call this correctly.

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?

There are no parameters, so the schema carries no burden. The description clarifies that the secret is 'presented' via Authorization, which is genuinely useful context for invoking the tool despite the empty 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?

The description clearly states a specific action ('Replace the presented secret') and resource ('caller key'), with the endpoint and behavior spelled out. It differentiates from siblings like revoke_key and issue_key by emphasizing that identity and credits are preserved while the secret changes.

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?

Provides concrete usage context: use Authorization: Bearer, X-API-Key is only an alias, and no ops file-edit is needed. It does not explicitly name alternatives or say 'use this instead of revoke_key', so it stops short of a full 5.

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