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

Beyond the read-only/idempotent annotations, the description discloses authentication requirements (API key, 401 without one), quota cost (1 read unit of the daily quota), retention behavior (newest 200 per account), paging limitations, empty-list behavior, and an error condition ('temporarily unavailable'). This is rich operational context 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?

Despite covering many operational details, the description is front-loaded with the core behavior and then adds constraints in a dense, purposeful sequence. Every sentence conveys distinct information about selection, paging, routing, or operational constraints.

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 moderate complexity, single optional parameter, existing output schema, and the rich annotations, the description covers everything an agent needs: what is returned, what is excluded, how to find a specific run, auth, quota, retention, and error behavior. No important gap remains.

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, but the description adds meaningful constraint semantics: 'limit takes only the newest runs' and 'There is no paging', clarifying how limit behaves in relation to retention. It does not define the exact integer bounds, but those are already in the schema.

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 states a specific verb and resource ('Lists the backtest runs on the API key's account') and enumerates the returned fields, including the key exclusion 'without trades'. It also distinguishes itself from both get_backtest and run_backtest, so an agent can route correctly without opening schemas.

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?

It gives explicit when-to-use guidance: find a backtest_id for get_backtest, compare earlier runs, or use run_backtest to start a new run. It also states the paging limitation and the alternative path (read a specific run by its id with get_backtest), leaving little to inference.

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