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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered; the description adds the non-obvious pagination contract (per_page plus start, next page at start + per_page) and the implicit 2019-08-01 lower bound on returned records, which the annotations do not convey.

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?

Three tightly packed sentences, front-loaded with the mode selection, followed by filters, pagination, and the underlying endpoint. Every sentence carries distinct information with 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 6-parameter read-only list tool with no output schema, the description covers filtering, defaults, and pagination well enough to call it correctly. The only gap is that it never hints at the shape of the returned invoice/estimate records, which no output schema supplies either.

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 the baseline is 3, but the description goes further by explaining the pagination arithmetic (next page = start + per_page) and restating the complete=true/false-to-invoices/estimates mapping in prose, which clarifies intent beyond the terse schema blurbs.

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?

Names a specific verb (List) and resource (invoices/estimates) and immediately disambiguates the dual mode via the complete flag, including which mode is the default. An agent can tell exactly what this returns without opening the 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?

The description supplies operating context (records created on or after 2019-08-01, optional closed_only and date-range filtering) but never says when to choose this tool over the sibling list_* tools or states any prerequisite. Usage is implied by the filter semantics rather than explicit.

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