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

Beyond the annotations (readOnly/openWorld/non-destructive), the description discloses ordering (newest first), item granularity ('Each item holds totals only', i.e. no line detail), a pagination ceiling ('Pages hold up to 100 purchases'), and an auth prerequisite ('Cotlet API key with access to this app'). These are meaningful behavioral facts not present in the structured fields.

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?

Five short sentences with no filler; the resource and its return shape are front-loaded, followed by usage, granularity, pagination and auth. The opening field enumeration is slightly list-heavy but still earns its place by previewing the row shape.

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, paged list tool with no output schema, the description supplies row contents, ordering, page sizing, filterable dimensions and auth requirements — everything an agent needs to call it correctly and interpret the result.

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 schema already documents from/to/paid/limit/cursor/supplier_id. The description reinforces the use of payment-status and date-range filters but adds no syntax or default detail beyond the schema, nor does it explain the cursor. Baseline 3 is appropriate when the schema carries the load.

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 ('Lists registered purchases') and immediately names what each record contains (supplier, date, invoice number, gross amount, unpaid amount) plus ordering ('newest first'). An agent can distinguish this read/list tool from the sibling create_purchase without opening any schema.

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?

Gives two explicit usage scenarios — 'to see what you still owe' and 'to check whether a supplier invoice number is already booked before create_purchase' — the second of which names the concrete alternative tool and the condition that calls for this lookup. Nothing is left to inference.

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