cancel_timer

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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the cancellation semantics are covered structurally, and 'cancel' is consistent with that. The description adds only the 'active' precondition; it says nothing about what happens with a stale or invalid ID or whether the operation is reversible.

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?

A single front-loaded sentence with zero padding. It could arguably carry one more clause (e.g. invalid-ID behavior) without becoming verbose, but nothing present is wasted.

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 annotations and no output schema, this is minimally sufficient — an agent can call it correctly. It is thin on outcome information, though: nothing about failure modes or how to obtain a valid timer ID (list_timers).

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% and the single 'id' parameter is already documented as 'Timer ID to cancel'. The description adds no format, source, or lookup detail beyond that, so the schema does all the work — baseline 3.

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 an active timer') scoped to a single timer 'by its ID', which implicitly separates it from the sibling cancel_all_timers. It never names that sibling explicitly, so differentiation is left to inference.

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 'an active timer' hints that only currently running timers are valid targets, but there is no explicit when/when-not guidance and no reference to cancel_all_timers as the bulk alternative. An agent must infer the boundary conditions.

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