read_parquet_preview_tool

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

Annotations already cover the safety profile (readOnly, openWorld, non-destructive), but the description adds real operational context: whole files are transferred within byte budgets (a cost/latency signal), no quality screening or time filtering happens (a caveat on what results mean), and the legacy s3_uri path returns migration guidance rather than data. That is meaningful disclosure beyond what the structured fields provide.

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?

Five short sentences, front-loaded with the core action and followed by input requirements and caveats. The 'Legacy s3_uri returns migration guidance' sentence is slightly tacked on but earns its place by warning about a deprecated input.

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?

An output schema exists, so return-value explanation is legitimately omitted, and the description covers the important behavioral caveats. For a 10-parameter tool with zero schema documentation, however, the parameter space is left substantially unexplained, so it is adequate but not complete.

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% across 10 parameters, so the description carries the entire burden — yet it only meaningfully touches file_url, s3_uri, and (vaguely) the partition filters and row bounding. Key parameters like inv_mode, freq_mode, max_files, and rows' exact semantics are undocumented in both the schema and the description.

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+resource combination ('Read actual Parquet schema and bounded rows') that clearly separates it from lighter-weight siblings like read_parquet_columns_tool, since it returns both schema and row data. It does not name a sibling explicitly, so the differentiation is inferred from the resource scope rather than stated.

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?

Tells the agent what inputs to supply ('an exact catalog-listed file_url, or storage partition filters'), which is genuine usage guidance for the two invocation modes. It does not say when to prefer this over listing or column-inspection siblings, nor what conditions should steer the agent away, so usage is implied rather than prescribed.

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