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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description's added value is the free-vs-paid cost model and the claim that argument checking matches the paid tool, which is genuinely useful. It does not say what a failed validation looks like or whether it costs anything server-side, though the output schema covers returns.

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?

One short sentence, front-loaded with the cost/purpose and ending with the sequencing cue. No filler, though it is arguably too terse for the schema complexity.

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?

An output schema exists, so return values need not be explained. But for a dedicated validation tool with a large nested input, the description says nothing about validation strictness, whether unknown fields fail, or what constraints are enforced (date ordering, stop ranges) beyond what the schema encodes.

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?

Eight parameters including a nested discriminated-union `strategy` object, with only 63% schema description coverage. The description provides zero parameter guidance, so the poorly described fields (date ranges, strategy params, universe interactions) are undocumented in both places.

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 the resource (backtest arguments) and the verb (check/validate), and explicitly ties it to the paid `backtest` tool, distinguishing it from that sibling. 'Check' is slightly soft about whether it returns validation errors, but the intent 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?

Gives a clear trigger: run this before paying for `backtest`. That is an explicit when-to-use relative to the sibling. It does not state when you can safely skip it (e.g. if you already know the args are valid).

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