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

Annotations already flag destructiveHint=true and idempotentHint=false, so the description's added value is the partial-cancellation semantics: recipients who already received the issue keep it, so the operation is irreversible-in-part. It does not mention whether the issue record is deleted, retained, or what the response contains.

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 very short sentences, front-loaded with the action, then the irreversibility caveat, then a cost note. Sentence fragments ('Free.') are terse to the point of being slightly cryptic, but nothing wasteful is present.

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-parameter mutation with annotations covering the safety profile, the description supplies the key missing behavioral fact (already-sent content cannot be recalled). Not covered: what state the cancelled issue ends in and whether in-flight scheduling is retried, but these are secondary given annotations and a fully documented schema.

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 issue_id parameter is fully documented in-schema, including its 36-character constraint and provenance. The description adds nothing beyond the schema, 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?

Uses a specific verb (stop/cancel) against a specific resource (an issue) and scopes it to scheduled or in-flight issues, which distinct it from newsletters_send_issue and newsletters_update_issue. It stops short of naming those siblings, so an agent must infer the boundary from the newsletters_ prefix.

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?

'Stop a scheduled issue, or one still going out' states the applicable conditions, and 'Whatever went out already stays sent' implicitly excludes already-delivered content from being recalled. No explicit redirection to an alternative tool (e.g. update_issue for a partial edit) is given.

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