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

The readOnlyHint=true annotation already covers the safety profile, so the description's job is lighter. It usefully adds the endpoint mapping (GET /invoice/{id}) and the shape of the payload (status, items, totals), but says nothing about not-found behavior, permissions, or error responses for an id that doesn't exist.

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 short sentences with zero filler: the operation and its return fields come first, the endpoint mapping second. Every clause earns its place.

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 no output schema, the description compensates by naming the key returned fields (status, items, totals), which is enough for an agent to know what it gets back. Minor gaps remain around error/empty cases for an invalid id, but nothing critical is missing for a single-parameter read.

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% and there is a single required integer id already documented as "The invoice id." The description restates "by id" without adding format, range, or sourcing guidance beyond what the schema provides, 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?

States a specific verb and resource ("Get one invoice by id") and enumerates the returned fields (status, items, totals), which distinguishes it from the many servicetrade_list_* siblings that return collections. It stops short of naming servicetrade_list_invoices as the alternative for finding an id, so it is clear but not maximally differentiated.

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 phrase "by id" implies the tool requires a known identifier, so the agent can infer this is a fetch-after-you-have-an-id operation rather than a search. However, no explicit guidance names servicetrade_list_invoices as the way to discover an id, and no when-not-to-use condition is stated.

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