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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description adds genuinely new behavioral context: the operation is free and requires no authentication, and it discloses the full content of the returned payload. It does not mention rate limits, caching, or error behavior for unknown IDs, keeping it below 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?

A single front-loaded sentence naming the resource first, then the payoff, then the cost/auth note. The enumerated list of returned artifacts is dense but every clause carries information; nothing is wasted.

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?

One required string parameter, no output schema — and the description compensates by listing the return contents and the cost/auth conditions. An agent has everything needed to decide and invoke 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?

Only one parameter exists with 100% schema coverage and an inline example (raw.douyin.video), so the schema carries the burden. The description's phrase "its parameters (JSON Schema)" refers to the endpoint's own parameter spec, not the endpoint_id argument, so it adds no semantics beyond the schema — baseline 3.

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?

Specific verb + resource ("Show one endpoint") plus an enumeration of exactly what the response contains (return shape, parameters, examples, price). It differentiates itself from the read-only siblings implicitly by covering a single endpoint in full, though it never names search_endpoints or call_endpoint.

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?

"Free; no sign-in required" gives a useful precondition, and the detail-heavy output description implies this is the 'inspect before you call' tool. However, there is no explicit guidance such as 'use search_endpoints to find an endpoint_id' or when to prefer call_endpoint, so routing is left to inference.

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