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

With no annotations, the description carries the full burden and usefully discloses the access model: pay 0.001 USDC via x402 or authenticate with an API key, including auto-pay and free API-key calls. It also says the response includes the execution config used, but it does not describe failure behavior for an unknown ID or broader return details.

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 purpose and usage guidance are front-loaded in the first two sentences, with payment/access details cleanly separated in a bracket. The text is appropriately sized and every part contributes useful selection or invocation context.

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 simple one-parameter retrieval tool with complete schema coverage and no output schema, the description covers purpose, sibling routing, payment/access, and that execution config is returned. It omits edge-case behavior such as what happens when the backtest ID is not found, but otherwise gives an agent enough to call it correctly.

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%, and the sole parameter is already documented as the run's UUID as returned by run_backtest. The description reinforces that the lookup is by id but adds no syntax or format detail beyond the schema, so the baseline of 3 is appropriate.

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: 'Fetch a backtest that already ran, by id, with the execution config it used.' It explicitly distinguishes itself from run_backtest, making the purpose unambiguous against a key sibling.

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: whenever the user refers to a previous result or wants to compare two runs, and explicitly says to use it instead of run_backtest in those cases. It also explains why re-running is undesirable by citing allowance cost and the stored record of what actually happened.

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