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

Despite annotations already covering the safety profile (readOnly=false, destructive=true, openWorld=true), the description adds substantial context: it spends AI-tester runs, does not change audience or questions, does not create a duplicate project, echoes designRefreshed: true, and returns the reused testId. This is behavior beyond what annotations 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?

The core purpose is front-loaded and nearly every sentence carries distinct information (cost, project reuse, uploadId behavior, audience caution, return values). It is dense and fairly long for a single paragraph, but there is little 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?

For a mutation tool with three params and an output schema, the description covers the essentials: what it mutates (spends tester runs), what it does not change, how to redirect it, and where results come from. An agent has everything needed to invoke it correctly.

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 0%, so the description must carry the load, and it does: projectId is defined as 'the testId from an earlier launch,' numTesters as optional testers for this run, and uploadId as an optional pointer to a newly prepared design snapshot with the resulting designRefreshed: true behavior explained.

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: 'Re-runs an existing usability-test project.' It explicitly names the siblings it differs from (propose_usability_test + launch_usability_test) and clarifies it reuses rather than duplicates the project, so an agent can distinguish it without opening any 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?

Gives explicit when-to-use and alternatives: use this to re-run on the same project, versus launch_usability_test to create a new one. It also routes related needs to revise_usability_test (audience changes) and prepare_design_snapshot/check_design_snapshot (updated design), and notes results come from wait_for_results or get_test_results.

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