Get invoice

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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds genuine context by stating that line items and the client relationship come back in the payload, which matters because no output schema exists; however, it says nothing about the include parameter's behavior, missing ids, or error cases.

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?

A single front-loaded sentence with the verb, resource, key selector, and return scope. No filler, no redundancy.

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 two-parameter read tool with full schema documentation and no output schema, the description covers what the call returns, which is the main gap it needed to fill. Only the include parameter's effect on the response is left entirely to the schema, a minor omission.

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%, so both id and include are already documented in the schema, including the 'client' default and the 'client,payments' example. The description's mention of line items and the client relationship loosely corroborates the default expansion but adds no new semantics beyond 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?

States a specific verb and resource ("Fetch a full invoice by id") and names the returned payload, which cleanly separates it from in_list_invoices. It stops short of naming the list sibling explicitly, so the differentiation is implied by "by id" rather than stated.

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?

Usage is only implied: an agent can infer this is the lookup-by-identifier path versus listing tools, but there is no explicit when-to-use or when-not-to-use guidance. Nothing tells the agent when to prefer in_list_invoices over this, or when fetching an invoice is unnecessary.

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