@readfetch/mcp-x402-proxy

readfetch_diff

Read-only

Detect URL content changes by sending a previous hash or text; returns changed/unchanged status and a bounded diff for review.

Instructions

Stateless change detection: send the hash you hold, get changed/unchanged and a bounded diff. A no-change answer is billable.

Input Schema

Name	Required	Description	Default
`url`	Yes
`format`	No		text
`timeout_s`	No	Total budget for the whole call in seconds, both fetches included. 60 s is the ceiling on this route.
`previous_hash`	No	sha256:... from a previous call.
`previous_content`	No	Previous text, for an added/removed diff.

Output Schema

Name	Required	Description	Default
`url`	No
`diff`	No
`hash`	No
`hint`	No
`added`	No
`billed`	No
`status`	No
`changed`	No
`removed`	No
`status_code`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv0.1.13Nov 1, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "added": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "billed": {
+      "type": "boolean"
+    },
+    "changed": {
+      "type": "boolean"
+    },
+    "diff": {
+      "type": "string"
+    },
+    "hash": {
+      "type": "string"
+    },
+    "hint": {
+      "type": "null"
+    },
+    "removed": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "status": {
+      "type": "string"
+    },
+    "status_code": {
+      "type": "integer"
+    },
+    "url": {
+      "format": "uri",
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

Changed3 schema fields changedv0.1.12Nov 1, 2026
- addedInput schema / properties / timeout_s / default
```
Added value: +30
```
- addedInput schema / properties / timeout_s / description
```
Added value: +"Total budget for the whole call in seconds, both fetches included. 60 s is the ceiling on this route."
```
- changedInput schema / properties / timeout_s / maximum
```
Previous value: -120New value: +60
```
First observedv0.1.0Nov 1, 2026

TDQS

A3.7/5.0

Behavior4/5

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

Annotations already cover readOnlyHint and openWorldHint, and the description adds genuinely non-obvious behavior: the call is stateless and a no-change answer is still billable. It stops short of explaining what 'bounded' means for the diff or how the two hash/content inputs interact.

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

Conciseness5/5

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

Two short sentences, front-loaded with the core contract and finished with the cost caveat. Nothing is wasted and no sentence restates the tool name.

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

Completeness3/5

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

An output schema exists so return values needn't be described, and billing is disclosed. Still missing for a 5-parameter tool: first-call behavior with a null previous_hash, whether previous_content is needed for an added/removed diff, and the meaning of 'bounded'.

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 60%, so the schema documents timeout_s and previous_hash/previous_content while url and format are bare. The description reinforces the 'hash you hold' idea but adds no meaning for format, the null-hash first call, or how previous_content differs from previous_hash.

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?

States a specific mechanism (stateless change detection via a supplied hash) and the outcome (changed/unchanged plus a bounded diff), which distinguishes it from readfetch_fetch or readfetch_text. It never names those siblings, so differentiation is inferred rather than explicit.

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?

'Send the hash you hold' implies the tool is for re-checks against a prior result, which is useful implied usage. However, it never states when to use this instead of readfetch_fetch, nor what to do on a first call when no hash exists.

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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