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

Goes well beyond the readOnlyHint/destructiveHint annotations: discloses Pacific Time and inclusive dates, that Google returns only top rows so results are always a subset, the meaning of all five data_availability states, that no_rows/access_error do not mean zero, and a prompt-injection warning about result strings. This is exactly the behavioral context structured fields cannot carry.

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?

Front-loads the purpose in the first sentence and every subsequent sentence carries distinct information (timezone, subset semantics, state meanings, safety warning). The inline enumeration of five data_availability values is dense and could be tightened, keeping it short of a 5.

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 fully carries the return-value burden, explaining the data_availability states, subset nature of results, and timezone of dates. Nothing an agent needs to interpret or correctly retry a call 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 coverage is 100%, so the baseline is 3, but the description adds genuine meaning the schema lacks: date inclusivity in Pacific Time and the relationship between data_state and the returned data_availability values. It does not explain row_limit/start_row paging behavior beyond what the schema already says.

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 (Read) and resource (Search Console performance) scoped to one site, and enumerates the exact metrics returned (impressions, clicks, queries). The scope and metric list make it unmistakable against the only nearby sibling, google__search_console__index_status.

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?

Provides operational guidance for the error state ('On no_rows, widen the date range and call again') but never states when to prefer this tool over alternatives or any exclusions. Usage is implied through the described result semantics rather than an explicit when/when-not rule.

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