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

The description discloses one behavioral trait: 'The body is discarded.' This implies the tool does not persist or modify input. However, with no annotations provided, the description carries the full burden of behavioral disclosure. It doesn't mention whether the tool is read-only, whether it makes network calls, or what side effects (if any) occur. The 'discarded' note is useful but insufficient for full transparency.

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, concise sentence that immediately states the core purpose. It avoids redundancy and is well-structured, with the key information front-loaded. No unnecessary words or phrases are present.

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 is incomplete for a tool with 9 parameters and no output schema. It doesn't clarify the role of the many seemingly unrelated parameters (city, feed, host, zone, query, etc.) or whether they are ignored. It also doesn't specify the return value or behavior beyond validation. For an agent to call this correctly, it would need to know what the tool returns (e.g., a boolean or an error message) and why those parameters exist, which the description omits.

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?

The schema has 100% coverage, with each parameter described in detail. The tool description adds no extra parameter semantics beyond what the schema provides. For example, the 'json' parameter is described as 'JSON text to validate; discarded after the check' in the schema, which is sufficient. The description itself doesn't explain parameter usage, but the schema does, so the baseline of 3 applies.

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's function: 'Check whether a body is valid JSON.' It uses a specific verb and resource, and it's distinct from siblings in that it validates JSON specifically. However, it doesn't explicitly distinguish itself from other validation-like tools (e.g., file-path-ok, domain-shape), relying on the name and simple description.

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 alternatives. It doesn't mention any conditions, prerequisites, or exclusions. The only hint is the name 'validate-json', which implies JSON validation, but there's no explicit comparison to similar tools or discussion of when not to use it.

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