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

With no annotations, the description carries the full behavioral burden and meets it: it discloses non-auto-paging, the 250 cap, paging.hasMore/nextOffset semantics, and the exact fields returned. It even warns about a false-negative conclusion, which is exactly the kind of behavioral trap an agent needs to know.

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 dense sentences: purpose and ordering first, then return shape and pagination behavior, then filtering guidance. No filler, no repetition of schema details.

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 list tool with no output schema or annotations, the description provides the essential missing context: output shape, key fields, pagination contract, and filter strategy. An agent can invoke it correctly and interpret results without further inference.

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. The description adds real value by explaining how limit/offset participate in paging, how offset should be fed from paging.nextOffset, and why milestoneId/createdAfter are preferable to paging. This goes beyond the schema's terse field descriptions.

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 first sentence names the exact operation ('List TestRail runs'), scopes it to a project, and specifies ordering ('newest first'). The return-shape detail and R-number id format make it unambiguous against siblings like testrail_list_tests_for_run or testrail_list_cases.

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 concrete usage guidance: use milestoneId or createdAfter to filter to a release/window instead of paging through history, and don't conclude a run is absent until paging.hasMore is false. It doesn't explicitly name alternative tools, but the tool's purpose and sibling set make that less necessary.

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