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

Annotations already cover read-only, idempotent and non-destructive semantics, but the description adds genuinely valuable behavior: the exact uptime formula, the exclusion of ERROR, MISSED and RATE_LIMITED runs, and the default 24-hour window. It does not describe response shape in detail, but for a read-only statistical tool this is strong added context.

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 short sentences with no waste: the core action, the formula/exclusions, and the default window are presented in a logical, front-loaded order.

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 read-only metric tool with no output schema, the description covers what is returned (uptime percentage, latency percentiles, run counts), how uptime is computed, which run statuses are excluded, and the default time window. Nothing essential for correct invocation is missing.

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 the schema already documents apiTestId, from and to including their defaults. The description reinforces the default-window behavior but adds no syntax or format detail beyond what the schema already provides; baseline 3 applies.

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 states a specific verb and resource: computing an API test's uptime percentage, latency percentiles and run counts. It is clearly distinct from raw-run siblings like get_api_test_runs in substance, but never names an alternative or explicitly contrasts itself with any sibling tool.

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 only implied: an agent can infer this is the aggregation/statistics tool rather than a raw-run fetcher, but there is no explicit when-to-use, when-not-to-use, or named alternative such as get_api_test_runs.

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