compare_runs

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds real value beyond them: no ranking is implied, last points may sit at different steps, data may be sampled, and returned training content is untrusted data rather than instructions. This is meaningful behavioral context an agent could not infer from the schema or annotations.

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 dense sentences, front-loaded with the core purpose and followed by caveats. Every sentence carries information, though the untrusted-data warning is slightly boilerplate-ish.

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?

The description usefully surfaces interpretation caveats for a no-output-schema tool, but with six parameters at 17% schema coverage and no output schema, key calling information (what stream/goal/limit do, what the response looks like) is missing. Adequate on caveats, incomplete on invocation.

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 only 17% (only run_uids and axis have descriptions), and the description adds nothing about goal, limit, stream, or metrics. With six parameters and this little schema documentation, the description should compensate but does not, leaving an agent to guess at the semantics of stream and goal.

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 ('Compare ... metric evidence across runs'), which separates it from siblings like get_metric_series or plot_metric. It does not name an explicit alternative, but the purpose is unambiguous.

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 implies a usage context ('Plot or export history to align budgets before claiming an improvement') and warns against over-interpreting results, but never states when to choose this over plot_metric or get_metric_series. Guidance is implied rather than explicit.

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