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

Goes well beyond the destructiveHint/idempotentHint annotations: it discloses immediate invalidation ('old token stops working at once'), a non-recoverable return ('new token is returned ONCE'), the signature requirement, and specific failure codes (signature_required, app_sign_in_only). This is exactly the consequence-level context annotations cannot express.

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?

Front-loads the action and the urgency, and every clause carries information (leak scenario, invalidation, one-time return, auth requirement, exclusion). Slightly dense with parentheticals but no filler sentences.

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 single-optional-param mutation with no output schema, it covers the prerequisite (signed request), the effect (old token dies), the return (token shown once), and the refusal modes. An agent has everything needed to call it safely or decide not to.

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?

Schema coverage is 100% so the schema carries the param, but the description adds real selection guidance — passport_token is a fallback used only when there is no app sign-in and no header — plus the header-vs-param distinction. That meaningfully exceeds the schema text.

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 and resource ('Replace your passport bearer token') plus a concrete motivating scenario. It is clearly distinguishable from siblings like revoke_passport or create_passport without opening any schema.

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?

Gives a clear trigger ('after it leaked') and an explicit exclusion ('a passport your MCP app signed in for has no bearer token and never gets one (app_sign_in_only)'). It does not name a sibling alternative (e.g., revoke_passport), leaving the routing mostly implicit, 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.