Retrieve an invoice

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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered. The description adds nothing beyond that — no statement about what is returned, what happens with a voided or nonexistent invoice, or any auth/rate considerations.

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?

The text is short and front-loaded, but it is effectively the same sentence twice, so the second sentence does not earn its place. Brevity here reflects under-specification rather than disciplined concision.

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?

This is a simple single-parameter read tool with rich annotations, but there is no output schema, so the description should at minimum sketch what a retrieved invoice contains. It also omits not-found behavior, leaving an agent with only the id format to go on.

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 a single parameter with 100% schema description coverage, so the schema carries the semantics and the baseline is 3. The description's mention of the `inv_…` prefix duplicates the schema text rather than adding new meaning.

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 restates the title and name almost verbatim: 'Retrieve an invoice' followed by 'Retrieve an invoice by id.' It does not differentiate this from siblings such as list_invoices, update_invoice, or finalize_invoice, nor does it say what an invoice retrieval returns or what scope it covers.

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, no mention of when to prefer list_invoices versus a single fetch, and no indication of prerequisites or failure conditions (e.g., unknown id). The only implied usage is that an id is required, which the schema already enforces.

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