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

Annotations already declare destructiveHint=true, readOnlyHint=false, and idempotentHint=true, so the safety profile is covered. The description adds genuinely new behavior: the no-op outcome for already-sent messages and the underlying DELETE endpoint. It stops short of noting failure behavior for an unknown id, so not a full 5.

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 tight clauses, front-loaded with the WRITE marker and the qualifying condition before the low-priority endpoint detail. Every sentence earns its place with no 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?

For a one-parameter mutation with no output schema, the description covers eligibility, no-op behavior, and the discovery path. It omits what the caller receives on success versus an invalid/already-sent id, which is a minor residual gap.

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?

With a single parameter at 100% schema description coverage, the schema already carries the meaning ('Scheduled message id.'). The description only echoes it via the DELETE path template and adds no format or constraint detail beyond the schema's numeric pattern.

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 scheduled, unsent message) and explicitly scopes what qualifies. The reference to trumpia_list_scheduled_messages lets an agent distinguish this from the listing sibling 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?

Gives an explicit when ('a message that is scheduled and has not been sent yet') and an explicit when-not ('Does nothing for a message already sent'), plus names the sibling used to discover candidate messages. Nothing about tool selection is left to inference.

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