Check authentication

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds useful context beyond that: it discloses that two distinct credential surfaces are validated (BigQuery API credentials and the Looker Studio browser session), which is the key thing an agent needs to interpret a failure. It does not describe the result shape, keeping it short of a 5.

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?

Two sentences, no filler, and the most actionable information (the "use first on auth errors" trigger) is placed at the end as a clear directive. Every sentence earns its place.

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?

There is no output schema, so the description carries the burden of explaining what the check returns (e.g., which surface passed or failed, or how to interpret a partial failure). It says what is checked but not what the agent will get back, which is a real gap for a diagnostic tool with no structured output.

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 tool takes zero parameters, so per the baseline this dimension starts at 4. There is nothing for the description to clarify beyond what the empty schema already conveys.

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 ("Check") and names the two concrete resources it validates: the Google API credentials (BigQuery) and the signed-in Looker Studio browser profile. This clearly separates it from the data-oriented siblings (run_query, list_reports, etc.), though it doesn't name any sibling explicitly.

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?

"Use first when other tools fail with auth errors" gives an explicit trigger condition that tells the agent exactly when to reach for this tool over retrying a failing sibling. It lacks a when-not clause, but the positive routing rule is unambiguous.

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