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

Annotations already declare destructiveHint=true, so the mutation profile is partly covered, but the description adds no behavioral context beyond that: it does not say builds consume build minutes/credits, are asynchronous, or require authentication. The only extra is the REST mapping 'POST /builds', which is marginal.

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 short sentences with requirements front-loaded ('appId and workflowId are required') before the optional surface. No redundancy or filler; every clause carries information.

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?

There is no output schema, yet a start-build tool's key output is the created build ID needed to poll codemagic_get_build or cancel it; the description never mentions what comes back or how to track the run. For a 7-parameter mutating tool with a nested object, that is a meaningful omission.

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 every parameter (including the nested environment object and instanceType examples) is already documented in the schema. The description merely restates required vs optional fields without adding format, allowed-value, or precedence detail, 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?

States a specific verb and resource ('Start a new build for an application workflow'), which cleanly separates it from siblings like codemagic_cancel_build and codemagic_get_build. The remaining sibling (e.g., list_builds) is not explicitly named, but the action is unambiguous.

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?

Notes the two required parameters and that branch/tag are alternatives for targeting a revision, which is actionable context. However, it gives no guidance on when to prefer starting a build here versus querying existing builds, and no prerequisites (auth, app/workflow must exist) are stated.

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