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

Annotations only give a generic mutation profile (readOnly=false, idempotent=true, non-destructive); the description adds the real behavioral payload: no email is sent, the candidate returns to their prior stage, and cancelled interviews are rebooked only if their time hasn't passed and the slot is free. It also discloses the terminal failure mode (email already sent). That is well beyond what the annotations convey.

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 eligibility condition is front-loaded and most sentences carry real information. Minor waste in the fragment 'Emails nobody.' and the inline get_candidate parenthetical, which reads like a note rather than routing guidance.

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?

An output schema exists, so return values need no explanation, and the mutation side effects and preconditions are fully covered. The one remaining hole is identifying which application_id is valid, which neither schema nor description resolves.

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 0% and both parameters (job_id, application_id) are bare strings with no descriptions. The description only indirectly hints at where the application comes from via get_candidate, and never clarifies the id formats or the job/application pairing, so it does not compensate for the coverage gap.

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 (cancel) on a specific resource (a rejection) plus the defining precondition: the email has not gone yet. This clearly separates it from reject_candidate in the sibling list, and an agent can distinguish the two without opening either 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?

Names when to use it (email pending), how to verify eligibility (get_candidate shows `pending_rejection` and when its email goes), and an explicit exclusion (a rejection whose email has gone cannot be cancelled). That is the full when/when-not/alternative triad.

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