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

Annotations already cover the safety profile (readOnly, non-destructive, closed-world), yet the description still adds genuinely non-obvious behavior: values are in cents, the result includes the invoice list, and null is returned for clients or when the client isn't invoiced. It does not describe the shape of the returned object, but with no output schema the null/units disclosures are the higher-value information.

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?

One compact sentence covering the returned fields, the unit, and the null cases. It is front-loaded with the payload content, though the elliptical phrasing ('null for clients or when the client isn't invoiced') reads slightly clipped.

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 one parameter at full schema coverage, annotations for safety, and no output schema, the description carries the return-value burden and does so: it explains the three numeric components, their unit, the accompanying invoices, and the null conditions. Nothing essential for a correct call is missing.

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 coverage is 100% and there is a single required requestId already documented in the schema, so the baseline is 3. The description only implicitly constrains it by scoping results to fixed-price requests; it adds no syntax or format detail.

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 the resource (a fixed-price request) and precisely enumerates the returned values: price, amount invoiced so far, and remaining balance, plus invoices. It is specific enough to distinguish from get_request or list_invoices, but it never explicitly contrasts with those siblings.

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 when-to-use guidance and no named alternative (e.g. list_invoices for invoice-only lookups). The only contextual hint is that it applies to fixed-price requests, which is left implicit about what happens for other request types.

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