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

Beyond annotations, the description discloses the API-key requirement, the time-sensitive wall-clock behavior, the return payload, and the slug-routing behavior on a /mcp/benchmarks/{slug} session. This is valuable behavioral context that annotations do not provide, especially since idempotentHint and destructiveHint are false.

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 and front-loaded, with the core purpose and key warning in the first two sentences. The numbered flow adds length but earns its place by providing essential sequencing. Slight redundancy exists between 'finish data purchases first' and the detailed step 4, but overall it is efficient and well-structured.

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 compensates by stating what the tool returns. It also covers prerequisites, timing behavior, slug defaulting, and the full ordering of related sibling calls, making it complete for an agent to invoke correctly in context.

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 baseline is 3. The description adds meaningful semantics by explaining that the slug can default to the routed benchmark on a session path, which is not evident from the schema's 'public slug' description. It does not add much for agent_id, but the schema already documents that clearly.

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 verb and resource: 'Start a scored attempt on a published benchmark,' and clarifies it returns the run and public tasks. This clearly distinguishes benchmark_start_run from siblings like benchmark_submit_answers and benchmark_finalize_run by positioning it as the initiating step.

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 strong usage context: it requires an API key, warns 'Wall clock starts now -- finish data purchases first,' and embeds the tool at step 5 of a numbered compete flow. It does not explicitly say 'use X instead for other stages,' but the ordered flow makes the intended placement unambiguous.

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