Validate a URL by checking protocol and SSRF safeguards without making a network request. Confirm safe, allowed URLs before fetching to prevent unsafe retrieval.
Validate a URL for webfetch (protocol + SSRF guard) without fetching it.
| Name | Required | Description | Default |
|---|---|---|---|
| url | Yes |
Changes observed during successful MCP inspections.
v1.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the burden, and it does disclose the two checks applied (protocol and SSRF guard) and that it is side-effect-free. However, it says nothing about the result shape (pass/fail, error detail) or how invalid URLs are reported, leaving meaningful behavioral gaps.
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?
A single front-loaded sentence with zero filler; the distinguishing clause 'without fetching it' lands immediately after the core purpose.
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, no-output-schema validator, the description covers purpose, scope, and the side-effect-free guarantee adequately. It could say a bit about the return outcome, but nothing essential for a correct call 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, self-evident 'url' parameter, but the schema has 0% description coverage and the description adds no semantics such as accepted schemes or length constraints (schema caps at 4096). The parameter is obvious enough that this is a minor gap rather than a blocker.
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?
Specific verb 'Validate' plus resource 'URL', with a parenthetical naming exactly what is checked (protocol + SSRF guard). It explicitly distinguishes itself from the webfetch sibling by stating 'without fetching it'.
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?
'without fetching it' clearly signals this is the dry-run/check-first option versus webfetch, giving an agent a workable when-to-use heuristic. It stops short of an explicit 'call before webfetch' rule or any when-not guidance, so it is clear but not exhaustive.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.