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

Annotations already cover safety (readOnly, idempotent, openWorld, non-destructive), yet the description adds substantial operational context beyond them: server-side pagination the caller never handles, a hard cap of 20 pages / 5000 tests, and the capReached flag that warns against concluding a test is absent. This is exactly the kind of behavior an agent needs and cannot get from structured fields.

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?

A single dense paragraph that is front-loaded with the core action and pagination guarantee, then the return shape, then filtering, then the cap caveat. Every sentence carries distinct, non-redundant information.

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?

With no output schema, the description steps in to describe the returned fields (T-id, C-id, title, status_id) and the capReached flag. Combined with the two-parameter schema and rich annotations, an agent has everything needed to call it correctly and interpret results.

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 adds real value: it enumerates the status code mapping (1=passed, 2=blocked, 3=untested, 4=retest, 5=failed) that is absent from the schema (0 enum parameters), and gives example filter values. It does not restate runId semantics, so it is not a full 5.

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?

States a specific verb and resource ('List EVERY test inside a TestRail run') and immediately distinguishes itself from sibling list tools like testrail_list_cases by scoping to a run. The mention that the underlying case_id should be fed to testrail_get_case clarifies its place in the tool chain.

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?

Gives a concrete when-to-use scenario ('list only failed tests when triaging') and routes the caller onward via the C-id to testrail_get_case. It lacks explicit when-not-to-use guidance or a direct contrast with testrail_list_cases / testrail_list_runs, so it stops short of a 5.

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