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

readOnlyHint=true already tells the agent this is a safe read, so the bar is lower. The description adds that related objects can be embedded inline (affecting payload size and shape), but says nothing about what fields are returned or whether a missing id errors versus returning null.

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?

One tight sentence leading with the core action, followed by a compact endpoint reference. Nothing is redundant and the most important information (single-project fetch, optional include) comes first.

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 two-parameter read-only lookup, the description covers the essentials and the annotations carry the safety profile. The only gap is return-value shape (no output schema exists), which the description leaves entirely unaddressed.

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 both parameters are already documented, including an example for `include` ('client or tasklists.tasks') that closely matches the description's example. The phrase 'for the whole task tree' adds a small interpretive gloss on nested includes, but it is largely repetition.

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 and resource ('Fetch one project') and immediately scopes it as a single-record read with optional inlined relations. The singular framing implicitly separates it from paymo_list_projects, and the API endpoint line grounds it further.

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?

Usage is implied by 'Fetch one project' with a required project_id, and the include examples show how to expand the response. However, it never states when to prefer this over paymo_list_projects or paymo_get_task, nor any precondition such as needing a known project id.

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