download_image

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

No annotations are provided, so the description carries full burden. It mentions the return value (local file path) but does not disclose overwrite behavior, directory creation, authentication requirements, error handling for invalid URLs, or whether the operation is synchronous. These gaps are significant for a mutation-like tool.

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 a single, clear sentence with a secondary sentence about the return value. No wasted words; essential information is front-loaded. Highly concise.

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 low complexity (3 simple parameters, no nested objects, no output schema), the description covers the core purpose and return value. However, it omits important details like default behavior for filename conflicts, directory creation, error outcomes, and supported file formats. It is adequate but could be more thorough to avoid ambiguity.

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 documentation coverage is 100% (all parameters have descriptions). The tool description adds no further explanation beyond stating the overall purpose. Baseline 3 is appropriate since the schema already explains each parameter adequately.

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 clearly states the action ('Download'), the resource ('an image from a URL'), and the result ('Returns the local file path'). It effectively distinguishes from sibling tools (image_search, web_search) which are search-oriented, not download-oriented.

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 implies usage when needing to save an image locally from a given URL. However, it does not explicitly state when not to use it or mention alternatives. The context of siblings being distinct search tools provides indirect guidance, but explicit usage conditions are absent.

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