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

The readOnlyHint annotation already covers the safety profile, and the description adds genuine value beyond it: it discloses that income invoices carry download_pdf_url and ephemeral_open_download_pdf_url and flags the latter as temporary. It stops short of describing error behavior or pagination-like concerns, but for a single-record get that's minor.

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, front-loaded with the core operation and followed by the one non-obvious return detail. No filler.

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 read-only single-record fetch with a fully described two-parameter schema and a clear readOnlyHint, the description covers what an agent needs plus a useful note on PDF link fields. The only gap is not-found/error behavior and the asymmetry for expense invoices.

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 invoice_id and include are documented structurally, and the description adds nothing about the include parameter or id format. Baseline 3 applies 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?

"Get one invoice by id" states a specific verb and resource, and the word "one" implicitly contrasts with quipu_list_invoices. It's clear what the tool does, though it doesn't explicitly name the list sibling as the alternative.

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: retrieve a single invoice when you already hold an id. There's no statement about when to prefer quipu_list_invoices instead, nor prerequisites or what happens with an unknown id.

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