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

Annotations already cover read-only, idempotent, and non-destructive, and the description adds meaningful context on top: an API key is required, there is no purchase/faucet/wallet cost, and gold answers and private task payloads are never returned. The negative disclosure about withheld data is exactly the kind of behavioral detail 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?

Front-loaded with the core action and cost stance, and the trailing caveats (slug default, withheld answers) are genuinely useful. Slightly dense with parentheticals and a spec reference, but no sentence is wasted.

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 read-only, two-parameter tool with no output schema, the description covers what is returned, what is not, auth needs, and cost, and the schema covers defaults. Adequate for correct invocation; only the absence of return-shape detail keeps it from a 5.

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 100%, so both the slug and agent_id parameters are already fully documented, including the routed-session fallback. The description restates the slug default behavior but adds no syntax or format detail beyond the schema, so the baseline 3 applies.

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 (get the benchmark's corpus) and enumerates exactly what it contains: the protocol doc plus case-packet documents of the exact data version. An agent can distinguish it from siblings like benchmark_get_results or benchmark_start_run 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 sequencing guidance ('Study it, then benchmark_start_run; wall clock starts at run start'), which tells the agent when this tool belongs in the workflow. It does not state explicit exclusions or conditions under which one would skip it, keeping it short of a 5.

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