fetch_url

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

The description discloses key behaviors: it saves a local snapshot with captured_at to prevent link rot, and the returned content_md is truncated by max_chars while full content is in the snapshot. Since no annotations are provided, the description fully carries the burden of behavioral 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 informative but somewhat verbose, mixing English and Chinese. It includes a typical usage flow that adds value, but could be streamlined. It is structured with clear sections but overall slightly long for a tool description.

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 complexity (external fetch, snapshot, truncation) and the presence of an output schema (so no need to detail return values), the description is complete. It covers purpose, behavior, usage flow, and parameter implications adequately.

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 coverage is 100% with descriptions for both params (url and max_chars). The description adds context: max_chars controls returned content length and that full content is in the snapshot, which is beyond the schema's default value and description. Baseline 3 plus extra value justifies 4.

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's action: 'Fetch a web URL and return its main content as markdown.' It emphasizes first-hand retrieval (G5) and distinguishes itself from siblings like save_research, which saves knowledge cards, and query_knowledge, which retrieves stored knowledge.

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 a typical usage flow: 'fetch_url to fetch primary source → write deep answer with specific numbers/mechanisms → save_research to save card.' It explicitly connects to the sibling tool save_research and implies when to use (before saving). However, it doesn't explicitly state when not to use or mention alternatives.

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