Fetch a public URL and return fetchability, size, final URL, title, and content hash without page content or payment. Start here before creating a monitor. Example: {"url":"https://example.com/"}.
| Name | Required | Description | Default |
|---|---|---|---|
| url | Yes | Public HTTP(S) page URL. No sign-in, cookies, browser rendering or private-network targets. |
Changes observed during successful MCP inspections.
Input schema / properties / url / descriptionAdded value: +"Public HTTP(S) page URL. No sign-in, cookies, browser rendering or private-network targets."Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already provide readOnlyHint, openWorldHint, idempotentHint, and destructiveHint. The description adds meaningful behavior beyond that: it fetches a remote URL, returns a summary of derived fields, and deliberately excludes page content and payment. This is useful contextual disclosure without contradicting the annotations.
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?
The description is two short sentences plus an example. It front-loads the core action and return fields, then adds the usage hint. Every sentence earns its place with no filler.
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 single-parameter read-only tool with strong annotations, the description covers the purpose, behavior, output fields, constraints, and usage sequence. No output schema is provided, but the listed return fields compensate. An agent can confidently call this tool correctly.
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 description coverage is 100% and the single 'url' parameter is already well described with constraints about public HTTP(S), no sign-in, cookies, or browser rendering. The description largely restates 'public URL' and adds an example, but does not add substantial new meaning beyond the schema.
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 names a specific verb and resource ('Fetch a public URL') and lists exact return fields: fetchability, size, final URL, title, and content hash. It also distinguishes itself by stating it returns no page content or payment, making its role unique among the sibling tools.
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?
The description explicitly says 'Start here before creating a monitor,' which gives a clear when-to-use signal and implies the tool is a prerequisite to fluxproof_create_monitor. It does not explicitly name alternatives or state when not to use it, so it stops short of a 5.
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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