Invoice

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered elsewhere. The description adds nothing beyond that – it does not explain caching behavior, why the `fresh` flag exists, or what the agent gets back. No contradiction with annotations, so not a 1.

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?

Two words is not conciseness but under-specification; there is no front-loaded verb or object to orient an agent. The brevity saves nothing because the content carries no information beyond the title.

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?

With only two params, full schema coverage and no output schema, a little description would suffice – but an agent still cannot tell from the description whether this returns an invoice object, a rendered document, or how it differs from the `invoices` sibling. Annotations cover safety, so the gap is small but real.

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% (both `invoiceId` and `fresh` are documented in the schema, including the cache-skip semantics of `fresh`), so the baseline is 3. The description contributes no additional parameter meaning, but it does not need to given the schema.

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?

"One invoice." merely restates the tool name/title in singular form. It never says whether it retrieves, renders, or summarizes an invoice, nor does it explicitly contrast with the sibling tool `invoices` – the singular/plural distinction is the only implicit differentiator an agent must infer.

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 whatsoever: no when-to-use, no when-not-to-use, no mention of the sibling `invoices` list tool, and no note that a valid invoiceId is required to fetch a specific record.

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