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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the mutation profile is covered. The description adds that cancellation applies only to scheduled sends before dispatch, which is useful context, but it does not disclose reversibility, idempotency, or the error behavior for already-sent emails.

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 sentence, front-loaded with the action and resource, no filler. Every word earns its place.

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?

Output schema exists and annotations carry the safety profile, so the description need not explain return values. For a one-parameter cancel operation it is nearly complete, with only edge-case behavior (already-sent, repeated cancellation) left unaddressed.

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 the single 'id' parameter is fully documented ('Email id (msg_…) of a scheduled send') including its format. The description repeats the scheduled-send qualifier but adds no new syntactic or semantic detail beyond the schema.

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?

Specific verb+resource: 'Cancel a scheduled email', with the scope constraint 'before it sends' clarifying that only pre-send scheduled emails are affected. It is distinguishable from siblings like send_email or get_email, though it does not explicitly name them.

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?

The phrase 'before it sends' implies the applicable condition, but there is no explicit when-to-use guidance, no statement of what to do if the email has already been sent, and no routing to sibling tools. Usage must be inferred.

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