fetch_url

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

With no annotations, the description carries the full burden. It discloses that a human approves each request and that the sandbox performs the fetch outside the agent's context, providing key behavioral context. However, it does not cover all potential behaviors like failure scenarios or rejection handling.

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 concise, with two short paragraphs that front-load the primary purpose and add key behavioral context without unnecessary words. Every sentence contributes value, making it well-structured and efficient.

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?

The tool is simple with only two parameters, and the description covers the main flow (fetch, approval, body). However, it omits the purpose of the 'reason' parameter, which is significant given zero schema descriptions. The output schema likely covers return format, but the missing parameter explanation creates a gap.

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 compensate, but it fails to explain the 'reason' parameter or any URL constraints. It implicitly mentions the URL but adds no meaningful detail beyond what the schema already shows (just types). The optional reason parameter is left unexplained.

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 tool fetches a URL through the sandbox, specifying both the verb and resource. It is distinct from siblings like run_privileged and request_path_access, making its purpose unambiguous and easy to differentiate.

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 fetch a URL and mentions human approval, but it does not explicitly state when to use this tool versus alternatives or specify exclusions. The guidance is implied rather than explicit, leaving some ambiguity.

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