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

With no annotations provided, the description carries the full burden and does disclose meaningful behavior: billing per the pricing sheet and that 'Denied requests never consume allowance.' However, it omits important side-effect details such as whether accepted requests mutate the ledger immediately, what permissions are required, and what the response looks like.

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 two sentences and front-loads the core action before billing details. Every sentence adds relevant information, and there is no redundant restatement of the tool name or schema.

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 involves metering, billing, allowance checks, and scope clamping, but the description does not explain return values or error behavior. With no output schema and 0% parameter description coverage, the definition leaves too much for the agent to infer before calling 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 description coverage is 0%, so the description must compensate for two parameters, including a nested request object. It only loosely identifies 'request' as a 'sampling/createMessage request' and 'server' as tied to a per-server ledger, without explaining the request object's structure or the server string format.

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 names a specific verb and resource: 'Meter one sampling/createMessage request against your per-server ledger.' It makes the core action clear, but it does not explicitly differentiate this tool from siblings such as guard_verdict or guard_policy.

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 explicit guidance on when to use this tool versus guard_ledger, guard_policy, or guard_verdict. The description implies it is for metering a single request, but it does not state prerequisites, exclusions, or alternative-routing conditions.

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