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

Annotations already declare destructiveHint=true, so the safety profile is covered. The description adds nothing beyond that: it doesn't say whether the cancellation is reversible, what build state results, whether artifacts are affected, or what error occurs for a non-running build. The REST endpoint line is metadata, not behavioral context.

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, action front-loaded, zero filler. Everything present earns its place, even if more could reasonably be said.

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 tool with destructiveHint annotations and no output schema, the definition is minimally viable: an agent knows what it does and that it is destructive. It is missing the post-condition and edge-case behavior that a cancel operation arguably warrants.

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% for the single buildId parameter, whose description already states 'The build id to cancel.' The description's 'by id' restates the schema rather than adding format or sourcing guidance, so the baseline 3 for full schema coverage 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 and resource ('Cancel a running build by id') and names the scope ('running'), which cleanly separates it from siblings like codemagic_get_build, codemagic_list_builds, and codemagic_start_build without needing to 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 'running build' implies a precondition, but there is no explicit when-to-use guidance, no statement about what happens if the build is already finished or invalid, and no reference to alternatives. Usage 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.