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

With no annotations, the description carries the full burden of disclosure. It does state 'The body is discarded,' which is a behavioral note about side effects. However, it does not mention whether the operation is read-only, what happens on success or failure, or how the other parameters behave. The parameter descriptions hint that each is discarded, but the tool description itself gives almost no behavioral context beyond the single sentence.

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 a single, compact sentence that front-loads the primary purpose and includes a note about disposal. It wastes no words and is easy to parse. However, it is arguably too terse given the tool's complexity, potentially sacrificing completeness for brevity, but that is more a completeness issue than a structure issue. The sentence is well-formed and efficient.

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 tool has nine parameters, no required parameters, and no output schema, making it quite complex. The description only addresses JSON validation and ignores the other eight parameters entirely. It does not explain when to pass a URL, a city, a feed, etc., or what the tool does with them. There is no indication of return values or error behavior. This is grossly insufficient for an agent to use the tool correctly beyond a trivial JSON check.

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%, so the schema already documents each parameter in detail. The description does not add extra meaning about parameter usage or relationships; it only refers to 'the body,' which loosely maps to the 'json' parameter. It does not clarify how multiple parameters interact or which parameter should be used for what scenario. Baseline 3 is appropriate because the schema is comprehensive, but the description adds marginal 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 states a clear verb and resource: 'Check whether a body is valid JSON.' That is specific and unambiguous for the JSON use case. However, the input schema exposes nine unrelated optional parameters (url, city, feed, host, path, zone, query) each with its own validation purpose, which strongly implies the tool may validate more than JSON. The description does not acknowledge this broader role, so it partially undermines clarity about what the tool actually does beyond JSON.

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 provides no guidance on when to use this tool versus the many sibling validators (e.g., browser-url-ok, normalize-url, weather-hint). It does not state that this tool is for JSON only, nor does it mention that other parameters are alternative validation modes. An agent cannot infer when to select validate-json over a sibling based on this description alone.

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