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

Annotations only declare the generic profile (readOnlyHint=false, openWorldHint=true, idempotentHint=false, destructiveHint=false). The description goes well beyond that: it discloses the session_token return value, instructs the caller to persist it, names every downstream tool that requires it, and imposes a credential-handling rule ('never print or log session_token; treat it like a password') that no annotation conveys.

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 compact sentences, fully front-loaded: precondition first, then the return value, then the downstream usage and safety rule. Every sentence carries operational information; nothing is 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?

With no output schema, the description takes on the burden of explaining the return and does so (session_token). For a non-idempotent, open-world auth step it covers precondition, result, downstream consumption, and secret handling — an agent has everything needed to call and use it 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?

Schema description coverage is 100%, so all three parameters (email, code, label) are already documented, including that email must match the auth_request_otp call. The description restates that intent but adds no format, constraint, or ambiguity resolution beyond the schema; the optional label is untouched. Baseline 3 applies.

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 states a concrete operation — exchanging an inbox code for a session_token — using a specific verb (verify/returns) and resource (one-time sign-in code / session). It also anchors the tool relative to auth_request_otp, so the agent can separate it from the other auth siblings without reading schemas.

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?

Explicit sequencing: 'right after auth_request_otp, with the code from the inbox.' It further tells the agent what to do with the result and which downstream calls (issue_agent_passport, get_agent_passport, update_agent_mandate, claim_agent_passport, refresh_claim_token) consume the token, which is unusually actionable routing guidance.

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