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

The readOnlyHint=true annotation already establishes the safe read profile, so the description only needs to add context. It does add value by enumerating what the response contains and citing the underlying endpoint, but it says nothing about failure behavior (e.g. what happens for a nonexistent id) or authorization scope.

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 a useful field list and no filler. The trailing 'GET /invoice/{invoice_id}' endpoint restates the tool name and the id parameter, so it is largely redundant rather than harmful.

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 correctly compensates by naming the main components of the returned invoice, which is the key completeness gap for a get tool. It is nearly complete, missing only error/not-found behavior and any auth or rate-limit context.

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?

There is exactly one parameter and schema coverage is 100% ('The invoice_id (a number).'), so the schema already fully documents it. The description's 'by invoice_id' adds no semantics beyond the schema, and the baseline of 3 is appropriate when the schema does the heavy lifting.

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 invoice_id') and enumerates the fields returned (status, line items, totals, balance, payments/credits, billing address), which makes the scope concrete. It distinguishes itself from the large family of list_* siblings implicitly via 'one invoice', but never names an alternative, so it stops short of full sibling differentiation.

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 single-entity variant of chargeover_list_invoices and should be used when an invoice id is known. There is no explicit when-to-use, when-not-to-use, or named alternative, which matters here given how many similarly shaped get_* / list_* siblings exist.

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