lookup_mime_type

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

No annotations are provided, so the description carries the full disclosure burden. It does this well by enumerating the full return dict including the 'found' key (implying graceful miss handling) and 'cost_usd' (signaling the tool has a monetary cost). It omits error behavior and rate limits, but for a single-query lookup this is a solid disclosure.

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 front-loaded with the purpose, then uses compact examples to convey format flexibility, then a tight Args/Returns breakdown. Every sentence earns its place; the example list is the most economical way to communicate the multiple accepted formats. No filler or redundancy.

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?

For a single-parameter lookup tool with no output schema, the description is nearly complete: input format, reverse behavior, and the full returned dict including cost are all specified. The only gap is explicit error-handling behavior, which the 'found' key mitigates. Minor omission given the tool's simplicity.

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 fully compensate — and it does. It defines the query parameter as 'File extension, filename, or MIME type string' and illustrates the acceptable formats with examples in both directions. Auto-detection between forward and reverse is made explicit, leaving no ambiguity about input.

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?

Description states a specific verb and resource ('Look up a MIME type by file extension or filename') and adds a reverse-lookup mode. Concrete input examples (png, .png, photo.png, archive.tar.gz, image/png) make the tool's scope unambiguous. No sibling tool overlaps in function, so differentiation is inherent but the description still pins the purpose precisely.

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?

The forward/reverse distinction with worked examples tells an agent exactly what to pass and what to expect back. There is no explicit 'when not to use' clause, but no sibling tool handles MIME types, so alternatives are not relevant. The guidance is implicit-but-strong through examples rather than explicit exclusion language.

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