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

Annotations already establish read-only, idempotent, non-destructive and closed-world, and the description goes well beyond them: no account required, no query cost, deterministic identical rows on every call, and the 20/100 limit behavior. The deterministic-sample caveat is a real behavioral trait an agent cannot infer from annotations or 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?

Dense but deliberate: purpose, exclusions, limits, determinism warning, and alternatives are all front-loaded and each sentence carries routing or behavioral information. The enumerated return fields are slightly long, but with no output schema they are justified.

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 supplies the return shape and explains the non-obvious fields (total_row_count is the whole table, sample_truncated). Combined with the alternative-tool routing and determinism warning, an agent has everything needed to call and interpret this tool.

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 0%, so the description must carry the semantics. It gives a concrete example object showing table_id as a UUID and limit usage, and states the 20 default and 100 cap. The default/max details duplicate the schema's default and maximum keywords, so it adds only modest meaning over the structured fields.

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 and resource ('materialized preview of a public table — real rows') and immediately separates itself from siblings by naming query_run, probe_source, and query_table with the conditions that select each. An agent can route correctly without opening any schema.

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?

Explicit when-to-use ('sample a source before anything is built' -> probe_source; 'filter, sort, aggregate or beyond the sample' -> query_table) and when-not ('Private workspace tables are not available here'). Alternatives are named with the exact condition that picks them.

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