cancel_scheduled_message

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

Goes well beyond the annotations by disclosing that the operation is local-only, that the job remains in the list with status 'cancelled', that it is irreversible without rescheduling, and that an error is returned when no pending job matches (already sent, failed, cancelled, or unknown). That is exactly the mutation/irreversibility 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?

One dense paragraph that front-loads the action and outcome, then layers id provenance, behavioral caveats, and return shape. No sentence 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 annotations covering the safety profile (destructive, idempotent, non-read-only) and no output schema, the description supplies the missing return shape and failure modes. Nothing an agent needs to invoke this correctly is absent.

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 already 100%, so the baseline is 3, but the description adds value by naming both source tools for the id and tying id validity to the error case. It still does not clarify whether the id is globally unique or per-account, so it stops short of 5.

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 ('Cancel one pending scheduled message') plus the outcome ('so it will never be sent'), which cleanly separates it from siblings like delete_message, schedule_message, and run_scheduled_messages.

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 the tools that produce the required id (schedule_message, list_scheduled_messages) and routes the agent away from re-activation ('cannot be re-activated; schedule it again instead'). It gives clear context but never states when this should be preferred over other message-removal tools such as delete_message.

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