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

Beyond the readOnly/idempotent/non-destructive annotations, the description discloses important behavior: it returns the oldest baseline, includes expired tests, and uses exact string equality matching on scheme, host, path, and trailing slash. This materially affects correct invocation.

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?

Every sentence earns its place: purpose, alternative tools, companion usage, and exact matching caveat. It is front-loaded with the core action and remains tightly organized without redundancy.

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?

Given a single required parameter, high schema coverage, an output schema, and annotations covering safety, the description supplies all needed selection and invocation context. It also routes to appropriate sibling tools for related use cases.

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 already documents the url parameter, so the baseline is 3. The description adds value by specifying exact string-equality semantics and trailing-slash sensitivity, going beyond the schema's 'must match the URL used when the test was run.'

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: 'Get the oldest baseline test snapshot for a single URL, including expired tests.' It clearly distinguishes this tool from related siblings by naming what it is not and how it differs.

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 explicit alternatives: use gvt_get_score_trend for pre-computed deltas, gvt_list_baselines for many URLs, and gvt_get_latest for comparison. It also advises discovering the exact URL form with gvt_list_tests when uncertain.

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