FreeTier Agent API

link-check

link_check

Read-only

3 free MCP calls per day (all tools together), then $0.0025 USDC via x402 or card credits (paid in-band: params._meta["x402/payment"]). Check up to 20 URLs in one call: HTTP status, final URL after redirects, redirect count, latency, content-type, ok flag. When to use: Use link-check to test up to 20 URLs for broken links in one call.

Input Schema

Name	Required	Description	Default
`urls`	Yes	comma-separated absolute URLs, max 20

Output Schema

Name	Required	Description	Default
`broken`	No
`checked`	No
`results`	No
`sources`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 26, 2026

changedOutput schema / description

Previous value: -"Inferred from a real response captured on 2026-10-24; extra fields may appear, null-valued fields are untyped."New value: +"Inferred from a real response captured on 2026-10-26; extra fields may appear, null-valued fields are untyped."

Changed1 schema field changedOct 24, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "description": "Inferred from a real response captured on 2026-10-24; extra fields may appear, null-valued fields are untyped.",
+  "properties": {
+    "broken": {
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "checked": {
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "results": {
+      "items": {
+        "properties": {
+          "content_type": {
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "final_url": {
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "ms": {
+            "type": [
+              "number",
+              "null"
+            ]
+          },
+          "ok": {
+            "type": [
+              "boolean",
+              "null"
+            ]
+          },
+          "redirected": {
+            "type": [
+              "boolean",
+              "null"
+            ]
+          },
+          "status": {
+            "type": [
+              "number",
+              "null"
+            ]
+          },
+          "url": {
+            "type": [
+              "string",
+              "null"
+            ]
+          }
+        },
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "sources": {
+      "items": {
+        "properties": {
+          "name": {
+            "type": [
+              "string",
+              "null"
+            ]
+          }
+        },
+        "type": "object"
+      },
+      "type": "array"
+    }
+  },
+  "type": "object"
+}

First observedOct 18, 2026

TDQS

A3.6/5.0

Behavior4/5

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

Annotations only declare readOnly/openWorld, so the description carries real weight and delivers: 3 free calls/day shared across all tools, $0.0025 USDC via x402 or card credits, and the in-band payment field path. That quota/payment disclosure is exactly the kind of context annotations cannot express, though timeout, redirect-following policy, and failure semantics remain unstated.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness3/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description opens with billing mechanics before saying what the tool does, which is poor front-loading for tool selection. The 'in one call' phrase and the 20-URL limit are each stated twice, so it is not wasteful but it is redundant and mis-ordered.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return fields needn't be explained, and cost, quota, and batch size are all covered. What is missing is operational behavior an agent would want before spending a paid call: per-request timeouts, whether redirect chains are followed by default, and how partial failures are reported.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% and the single param already documents 'comma-separated absolute URLs, max 20', which the description merely repeats. Baseline 3 is appropriate since the schema does all the work and the description adds no syntax or edge-case detail.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

Specific verb+resource with an enumerated output set: 'HTTP status, final URL after redirects, redirect count, latency, content-type, ok flag' tells the agent exactly what it gets back. It does not distinguish itself from nearby siblings like page_check or robots_check, which also touch URLs, so an agent still has to infer the boundary.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The 'When to use' clause gives a use case (broken-link testing, up to 20 URLs in one call), but it only restates the capability line rather than adding a decision rule. There is no when-not guidance and no mention of page_check/robots_check as alternatives for single-page or crawler-rule checks.

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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