fetch_url

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

With no annotations, the description carries the full burden and does so well: it discloses the output form (cleaned, untrusted text), security constraints (internal addresses and downloads blocked, prompt-injection content filtered), and a usage caveat (treat text as data, not instructions). This is behaviorally rich relative to the absence of structured hints.

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?

Three tight sentences with zero padding. The core action is front-loaded and each following clause adds a distinct, useful fact (blocking rules, then the injection-safety instruction).

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 one-parameter fetch tool with no output schema, no annotations, and no siblings, the description supplies everything an agent needs: input expectation, security constraints, and how to treat the return value. Nothing material is missing.

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?

There is a single parameter and schema description coverage is 100%, so the schema already documents the 'url' field. The description adds no format, scheme, or validation detail beyond the schema, so the baseline of 3 applies.

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?

States a specific verb (fetch) and resource (a public web page) and further qualifies the output as 'cleaned, untrusted text'. There are no siblings to distinguish from, but the scope is unambiguous and an agent knows exactly what the call produces.

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?

Usage is implied (fetch a page when you need its text) and the description hints at constraints by noting it blocks internal addresses, downloads, and prompt-injection content. However, it never states when to use this versus any alternative or what conditions would make it fail, so guidance is only implied.

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