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

Annotations already declare readOnlyHint=true, and the description reinforces a safe GET operation with the Quaderno API endpoint. It adds useful behavioral context by disclosing the full response scope (items, taxes, payments, permalink, pdf), which goes beyond the minimal read-only signal. No contradiction exists.

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 description is a single sentence that front-loads the core purpose, then efficiently adds response-content detail and an API reference. Every word earns its place with 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 simple single-invoice fetch with one required parameter and readOnlyHint=true, the description provides all necessary context: the target resource, the identifier, and the expected response contents. No output schema exists, so the explicit mention of included fields is especially valuable.

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%, so the single 'id' parameter is already documented as 'The resource id.' The description confirms retrieval by id but adds little semantic meaning beyond what the schema provides. Baseline 3 is appropriate.

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 uses a specific verb ('Fetch'), a clear resource ('a single invoice by id'), and adds detail about what the full object includes (items, taxes, payments, permalink, pdf). This clearly distinguishes it from sibling list operations like list_invoices and other single-resource getters like get_credit_note.

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 'a single invoice by id' clearly communicates when this tool is appropriate: retrieving one specific invoice rather than listing invoices. It does not explicitly mention alternatives or exclusion conditions, but the context is clear enough for an agent to select it correctly among related tools.

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