Upload file to Gemini Files API

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

Annotations provide readOnlyHint=false (indicating mutation) and openWorldHint=true (suggesting external API interaction). The description adds valuable context beyond annotations: it specifies the API target ('Gemini Files API'), mentions file size constraints ('larger than 20MB'), and describes reuse scenarios. No contradiction with annotations exists.

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 extremely concise (two sentences) with zero wasted words. The first sentence states purpose and return value, the second provides usage guidelines. Every element serves a clear purpose, and information is front-loaded appropriately.

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 the tool's moderate complexity (file upload to external API), annotations cover safety aspects, and the description adds practical usage context. The main gap is lack of output schema, but the description mentions return values ('URI & metadata'). For a mutation tool with external API interaction, this is reasonably complete though could benefit from more behavioral details like error handling.

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?

With 100% schema description coverage, the schema already documents both parameters thoroughly. The description doesn't add any parameter-specific information beyond what's in the schema (e.g., it doesn't explain path format constraints or display name usage). This meets the baseline for high schema coverage.

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 action ('Upload a local file') and target ('Gemini Files API'), and specifies the return value ('return its URI & metadata'). It distinguishes from sibling tools like 'generate_image' by focusing on file upload rather than image generation. However, it doesn't explicitly differentiate from other potential file operations beyond the scope of provided siblings.

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 description provides explicit usage guidance: 'Useful when the image is larger than 20MB or reused across prompts.' This gives clear criteria for when to use this tool versus alternatives (e.g., for large files or repeated use cases), though it doesn't name specific alternative tools since none are provided in siblings.

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