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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so safety is covered. The description adds meaningful behavioral context beyond that: the full 1–7 type mapping, the fact that results come 'from the books', and the authentication requirement ('Needs the user's Cotlet API key with access to this app'). Pagination behavior is not described, keeping it below a 5.

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 definition is front-loaded with purpose before the type enumeration and usage note. The type list is verbose but each entry is load-bearing given the useless schema enum; 'Returns mutations from the books' is the one mildly redundant sentence.

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, non-required-parameter list tool with no output schema, the description covers purpose, filtering dimensions, type semantics, usage intent and auth needs. It omits any mention of paging behavior, but limit/offset are self-documented in the schema, so nothing critical is missing.

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 baseline is 3. The description earns above baseline by supplying the actual semantic meaning of the 'type' values (1 invoice received through 7 general journal entry), which the schema enum fails to convey — the enum literally reads '1 to 7'/'see details', so the description is the only useful source for that parameter.

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 states a specific verb and resource ('Bookings (mutations) filtered by type, date, invoice number or description') and scopes the result set precisely. An agent can distinguish this from the sibling list tools (list_invoices, list_relations) because it operates on the mutations ledger and enumerates the mutation types.

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?

It gives a concrete use case ('Use it to see whether a payment is already booked'), which tells the agent when this tool is appropriate. It stops short of naming when-not-to-use or pointing to alternative sibling tools (e.g. list_outstanding_invoices), so it is clear context without exclusions.

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