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

No annotations are provided, so the description carries the full burden. It transparently discloses that without a subscription, it returns a delayed sample, and with a subscription, live data. It also mentions pricing and payment via x402, which is important behavioral context. However, it doesn't mention rate limits or error behaviors (e.g., what happens if endpoint is invalid), so not a 5.

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 description is reasonably concise, starting with the key differentiator (free delayed sample) and then explaining live data. It mixes pricing and usage, which is a bit dense but each sentence earns its place. Front-loading the key 'FREE' element is effective. Slightly overlong with the URL and pricing details, but still well-structured.

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 provides the essential information for calling this tool: how to get the endpoint, the free vs. paid behavior, and the response shape visibility. It doesn't describe the return format or pagination, but there is no output schema, so that could be a gap. However, given the tool's simplicity (just two parameters), this is fairly complete for an agent to decide to call it.

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 schema already describes both parameters adequately. The description adds context about the endpoint coming from search_market_data, which is helpful but does not detail parameter formats beyond the examples. Baseline 3 is appropriate as the description offers marginal added value.

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 clearly states the tool fetches data from an endpoint returned by search_market_data, distinguishing it from siblings. It specifies the resource (data endpoint) and the verb (fetch), and even mentions that endpoint comes from search_market_data, which is the only sibling it relates to. It could be more explicit about what 'data' means (e.g., time series vs. snapshots) but the core purpose is clear.

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 explains when to use it: after search_market_data returns an endpoint, and contrasts live vs. delayed data based on subscription. However, it doesn't explicitly say when NOT to use it or when to use alternatives like market_snapshot. The guidance is contextual but lacks explicit exclusions, so a 4 rather than 5.

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