free_url_checkFREE — FREE: check whether a public URL is reachable and what it is. Returns HTTP status, final URL after redirects, content type and page title. Use web_fetch (paid) for full text and links.
| Name | Required | Description | Default |
|---|---|---|---|
| url | Yes | Target URL; protocol optional |
Changes observed during successful MCP inspections.
Input schema / properties / qRemoved value: -{
- "description": "JSON or key=value input for the tool",
- "type": "string"
-}Input schema / properties / urlAdded value: +{
+ "description": "Target URL; protocol optional",
+ "type": "string"
+}Input schema / requiredAdded value: +[
+ "url"
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden, and it does disclose the return shape, redirect-following behavior, and the free/paid cost model relative to web_fetch. It stops short of stating timeouts, rate limits, or whether private/non-public URLs are rejected, which matters for a network-egress tool.
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 short sentences, front-loaded with the purpose and return values before the alternative. The doubled 'FREE — FREE:' prefix is redundant noise that costs a little precision.
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?
There is no output schema, but the description compensates by enumerating the returned fields, and the single-parameter surface is fully documented in the schema. For a one-arg read-only probe this is close to sufficient, with only failure/edge-case behavior left implicit.
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% for the single 'url' parameter, so the baseline is 3. The description's 'public URL' wording adds a mild constraint the schema lacks (schema only notes protocol is optional), but no format or syntax detail 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 and resource ('check whether a public URL is reachable') and enumerates the exact payload returned (HTTP status, final URL after redirects, content type, page title). That enumeration distinguishes it cleanly from web_fetch and web_brief among the siblings.
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?
It names the alternative explicitly — 'Use web_fetch (paid) for full text and links' — and gives the condition that selects it, so an agent can route between a cheap reachability probe and a full-content fetch without guessing. The 'FREE' marker adds a cost dimension to the decision.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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