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FetchDelta

by com.fetchdelta
OverviewDiscussionsAdmin

preview_page

Read-onlyIdempotent

Free: preview readability of one public HTML page before purchasing. Truncated Markdown only; no JavaScript or login bypass.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "url": "<url>"
    },
    "name": "preview_page"
  }
}

Input Schema

NameRequiredDescriptionDefault
urlYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observed

TDQS

A3.9/5.0
Behavior4/5

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), and the description adds real behavioral context the annotations cannot: output is truncated Markdown, JavaScript is not executed, and login-gated pages are not bypassed. It stops short of describing truncation length or rate limits for the free tier.

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 compact sentences with the free/preview framing front-loaded and the limitations packed into the second clause. No filler.

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?

With no output schema, the description correctly discloses the return shape (truncated Markdown) and the two key capability limits. A minor gap remains around truncation size and error behavior for non-HTML or blocked pages.

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

Parameters4/5

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

Only one parameter with 0% schema description coverage, so the description must carry the load. It meaningfully constrains the url to a single public HTML page, telling the agent that authenticated or JS-rendered targets are invalid inputs, which is more than the schema's bare 'uri' type conveys.

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 verb and resource: preview the readability of one public HTML page. The 'Free' and 'before purchasing' framing signals this is a trial of a paid fetch/resolve capability, which helps place it among siblings, though no sibling is named explicitly.

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?

Usage is implied rather than stated: 'before purchasing' suggests evaluating a page prior to committing, but it never names the paid alternative (e.g. resolve) or says when this tool is inappropriate beyond the negative constraints.

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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