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

Annotations declare the mutation and idempotency profile, and the description adds the key behavioral precondition that cancellation only works before dispatch — a state constraint annotations cannot express. It does not say what happens on a failed attempt (error vs no-op), which would complete the picture.

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?

Two short sentences: the action and its precondition up front, then the exclusion. Nothing redundant or padded.

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 and annotations cover idempotency and mutation semantics, so the description needn't explain return values. It supplies the crucial timing constraint; only the failure behavior for a missed window is left unstated.

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% and the single `id` parameter is already documented in the schema, including its origin ('from send_sms'). The description adds no parameter-level meaning beyond that, so the 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?

States a specific verb (cancel) and resource (a text) plus the scope of applicability. The purpose is unambiguous and clearly distinct from sibling tools like send_sms or get_message, though differentiation is left implicit rather than stated.

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?

Explicitly gives the eligibility condition — still 'scheduled or waiting for the phone' — and the exclusion — 'dispatched or sent' can't be cancelled. No alternative tool is named, but none is plausibly needed for this operation.

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