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

Annotations already declare readOnly=false, destructive=false, openWorld=false, but the description adds genuinely new behavior: asynchronous execution, a returned jobId, the required polling step, and that the status lists failing tests. That is real context beyond the annotations, though permission/auth requirements are not mentioned.

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, each earning its place: what it does, the async job contract, and the polling target. The async nature of the operation is front-loaded immediately after the purpose.

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?

With no output schema, the description correctly compensates by explaining the return value (jobId) and the follow-up status call that reports failing tests. It is essentially complete for invocation, missing only device/destination defaults that the schema partially covers.

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 67%, so most parameters are documented in the schema. The description implies the 'scheme' and simulator/device selection but adds no syntax or default guidance for parameters like destination, configuration, or workSessionId. Baseline 3 is appropriate given the moderately self-documenting schema.

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 ('Run a scheme's tests on an iPhone simulator on this Mac') and clearly distinguishes itself from sibling ios_build by describing the test-run job model. An agent can tell what this does without opening the 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?

Explicitly tells the agent this runs as a background job, returns a jobId, and that the agent must poll ios_build_status with that id. This is clear operating context, though it does not explicitly contrast when to use this versus ios_build or ios_archive.

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