query

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

With no annotations, the description carries the full burden. It discloses two important behavioral traits: only SELECT queries are allowed and a LIMIT clause is automatically added if missing. It also sets expectations for careful analysis. This provides meaningful behavioral context beyond the schema.

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?

The description is concise and front-loaded, with the primary purpose in the first sentence. Each subsequent sentence adds value—constraints, workflow, and analysis guidelines. The IMPORTANT section is somewhat verbose but contains critical guidance. Overall, it's efficient without being excessive.

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 that this is a complex SQL query tool with no output schema, the description is quite complete. It covers security constraints, automatic LIMIT addition, required schema exploration, and proper data interpretation. It doesn't address potential pitfalls like query errors or timeouts, but it provides sufficient context for an agent to use it effectively.

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. The description adds some context around the sql parameter (SELECT-only) and the LIMIT behavior, which indirectly relates to max_rows. However, it doesn't provide significant enrichment beyond what the schema already describes for each parameter.

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 clearly states the tool's purpose with a specific verb and resource: 'Run a SQL query against BigQuery and return results.' It adds the key constraint that only SELECT queries are allowed, which further clarifies scope and distinguishes it from general data manipulation tools.

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?

It provides a clear workflow: use list_datasets, list_tables, and describe_table first to understand the schema. It also instructs the agent to base analysis only on returned data and to state when data is insufficient. While it doesn't explicitly mention alternative tools like sample_rows or query_cost_estimate, the workflow guidance is strong.

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