fetch_url

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

With no annotations provided, the description carries full burden and does well by disclosing key behaviors: automatic rendered fetch for JS-heavy pages, browser mode activation, and the return format (compact excerpt with hidden full text metadata). It doesn't mention rate limits, authentication needs, or error handling, but covers core operational traits.

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?

Two tightly constructed sentences with zero waste. The first sentence covers the core functionality, and the second provides specific operational guidance. Every word earns its place, 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?

For a 6-parameter tool with no annotations and no output schema, the description provides good operational context but leaves gaps. It explains the core behavior and one parameter's purpose, but doesn't cover return format details, error conditions, or the semantics of most parameters. Given the complexity, it's adequate but incomplete.

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 0% schema description coverage, the description compensates by explaining the purpose of the 'rendered' parameter and implying URL fetching behavior. However, it doesn't address the semantics of other parameters like 'max_excerpt_chars', 'max_links', 'render_wait_ms', or 'ttl', leaving some gaps in parameter understanding.

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 purpose with specific verbs ('fetch', 'extract', 'return') and resources ('URL', 'readable content', 'compact excerpt'). It distinguishes from siblings like 'search' or 'fetch_many' by focusing on single URL processing with content extraction features.

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 clear context about when to use certain features ('rendered=True to force browser mode' for JS-heavy pages), but doesn't explicitly state when to choose this tool over alternatives like 'search_and_fetch' or 'fetch_many'. It gives operational guidance but lacks sibling differentiation.

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