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

Beyond the annotations, the description discloses that an API key is required, that the run is timed ('Wall clock starts now'), and that the call returns both the run and public tasks. It also reveals the purchase-gate prerequisite of at least one completed query. This adds meaningful behavioral detail that annotations alone do not provide.

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 description is dense but well-organized, front-loading the core purpose and key warning before the ordered flow. The numbered step list makes the prerequisite chain easy to follow, and every sentence adds useful information rather than padding.

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?

Given the tool's complexity, timed side effects, prerequisite chain, and lack of an output schema, the description is complete enough to use correctly. It covers the required API key, the return value, the wall-clock behavior, the slug default, and the full surrounding workflow.

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?

The schema already provides descriptions for both parameters, including the optional agent_id. The description adds extra semantic context by noting that on a /mcp/benchmarks/{slug} session the slug defaults to the routed benchmark. Since schema coverage is 100%, this is a solid score above 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?

The description opens with a specific action and resource: 'Start a scored attempt on a published benchmark.' It also states what the call returns ('the run plus this attempt's public tasks'), which clearly differentiates it from siblings like benchmark_submit_answers or benchmark_finalize_run. The purpose is unmistakable.

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 description gives explicit usage context: it must be called after data_session_query and before benchmark_submit_answers, and it lists the full ordered compete flow. It also warns 'finish data purchases first' because the wall clock starts now. This is strong when-to-use guidance with concrete prerequisites.

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