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

With no annotations, the description carries the full burden of behavioral disclosure. It only mentions 'body discarded', which hints at a non-intrusive operation, but it does not disclose whether the tool is read-only, what it outputs, whether it makes network calls, or any side effects. This is a significant gap for a tool with zero annotation coverage.

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 extremely brief (one short phrase), which could be seen as concise, but it lacks any structure or explanatory content. It is under-specification rather than efficient conciseness; a single vague sentence does not earn its place because it conveys almost no useful information.

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?

For a tool with 9 optional parameters and no output schema, the description is grossly incomplete. It does not explain the tool's purpose, expected inputs, return values, or relationship to siblings. An agent would have no idea what a successful call looks like or what to do with the result. This is far below the minimum viable description for such a complex tool.

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 provides 100% coverage with a descriptive one-liner for each of the 9 parameters. The description adds no extra parameter semantics beyond the schema, so the baseline of 3 is appropriate. It neither clarifies nor contradicts the schema's parameter documentation.

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 'Cap'n Proto segment count, body discarded' is a noun phrase that names a format and a metric but lacks an explicit verb or resource. It is not a tautology, but it does not clearly state what the tool does or what it returns, making it hard for an agent to understand the intended operation. It offers little to distinguish it from sibling shape/validation tools without opening the schema.

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?

There is no guidance on when to use this tool versus the many siblings like 'domain-shape', 'validate-json', or 'fetch-status'. No context, no alternatives, no exclusions are provided, leaving the agent to guess the appropriate invocation scenario.

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