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

Annotations declare this is a non-read-only, non-idempotent, non-destructive write, and the description adds genuinely useful behavior beyond them: that a release build consumes one build from the plan quota and that release output is signed and lands in TestFlight. It omits failure/log-retrieval behavior, but the quota cost is meaningful context annotations cannot convey.

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, front-loaded with the action and followed by the mode distinction and the polling hint. No filler and no redundancy.

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?

An output schema exists, so return values need no explanation, and the description covers the two modes, their side effects, cost, and how to check progress. It leaves unanswered what happens on a failed build and which sibling exposes build failures, which would round it out.

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%, so the schema already documents project_id, workflow, and the request_key reconcile semantics in detail. The description largely restates the workflow definitions the schema already provides, adding little beyond the baseline.

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+resource ('Start a build for a project') and immediately subdivides into two named modes, release vs smoke. It is clearly distinguishable from peers like push_project or publish, though it never explicitly contrasts itself with 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?

Gives clear selection context for the two workflows (signed TestFlight upload vs unsigned compile check) and routes the agent to the 'status' sibling for polling. It stops short of stating when not to use the tool or how it relates to publish/push_project in a full workflow.

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