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

Annotations already mark it read-only and idempotent, and the description adds valuable behavioral detail: the 200-item max limit, pagination fields in the response, and the meaningful empty-list case. This goes beyond what annotations convey and helps an agent interpret results correctly.

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 dense sentences: the first states the operation and domain, the second covers limits, response fields, empty-result semantics, and a pointer to the sibling creation tool. No filler or repetition of annotation facts.

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 read-only list tool with annotations and an output schema, the description covers the essential operational details: what is returned, paging constraints, empty-list interpretation, and next step. Nothing critical is missing for an agent to invoke it correctly.

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?

The schema documents limit and offset, including the no-cursor paging approach, so the description does not need to repeat those. However, project_id is not described in the schema, and the description only indirectly implies it via 'for a project'. The description adds the response-pagination context but doesn't fully compensate for the undocumented project_id beyond what the tool name suggests.

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 ('List') and a clear resource ('fixed-fee billing milestones for a project'), and explains what the billing plan represents (the instalment plan for a fixed-price project). This clearly distinguishes it from sibling billing-milestone mutation tools and from other project getters.

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 gives clear context: it is a listing operation for a project's fixed-fee milestones, and an empty list is explicitly interpreted as 'no plan has been built yet'. It also points to the sibling creation tool. It does not explicitly state when not to use it relative to broader invoicing/finance getters, but the context is strong.

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