validate_url

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the read-only nature is covered. The description adds useful detail about the specific checks (syntax, resolution, SSL status, response code, response time), which implies live network requests. However, it does not explicitly state that the tool performs outbound HTTP calls or that it could be slow or fail due to network issues. This is additional context that would help the agent set expectations, but it is not critical given the annotations.

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 two sentences, front-loaded with the primary purpose ('Validate a URL's format and reachability') followed by a concise list of checks. There is zero fluff, and every word contributes to the meaning. It is an exemplary model of concise, structured 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?

For a single-parameter, read-only tool with no output schema, the description is mostly complete. It explains what the tool does and the checks performed. The main missing element is the return format or a note that it makes live network requests, which could affect runtime expectations. However, given the tool's simplicity and the annotations covering safety, the description is adequate. It is slightly above the minimum because it provides a clear list of what is validated.

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?

The input schema has 100% description coverage for the single parameter 'url,' including an example. The description does not add any information about the parameter beyond what the schema already provides. Per the rubric, with high schema coverage the baseline is 3, and the description does not go beyond that.

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 states a specific verb ('Validate') and resource ('a URL'), and clearly defines the scope as 'format and reachability,' then enumerates the checks performed (syntax, resolution, SSL status, response code, response time). This is a clear, specific purpose. However, it does not explicitly differentiate from sibling tools like check_ssl or check_performance, which could cause ambiguity about when to choose this tool over a more specialized one.

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?

There is no guidance on when to use this tool versus alternatives. The description does not mention any exclusions, alternatives, or prerequisites. While the purpose implies a general URL validation use case, the lack of any explicit 'use this when...' or 'for SSL-specific checks, use check_ssl' leaves the agent without routing context. Given the many related siblings (check_ssl, check_performance, trace_redirects), this is a significant gap.

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