MCPFax URL Intelligence

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

With no annotations, the description carries the disclosure burden. It usefully discloses that the tool is free, returns an aggregate rather than individual requests, sorts by demand, and includes categories with nothing available yet. It does not explicitly state read-only behavior, but for a report tool this is a minor gap.

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 short but not fully polished: 'FREE, no payment' partly repeats the title's '(free)', and the phrase 'categories nothing available yet serves' is awkward. It is still compact, but the wording could be clearer.

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 simple one-optional-parameter report with no output schema, the description provides enough context: it explains the free aggregate output, the ordering, and the inclusion of unserved categories. The remaining detail about the days parameter is covered by the schema.

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?

The input schema already fully documents the only parameter: days window, default 30, max 90. The description itself adds no parameter-level meaning, so the baseline of 3 applies.

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 identifies the resource as an aggregate of what agents are looking for, states the ordering ('most-requested first'), and mentions unserved categories. This distinguishes it from the package_* siblings, though it does not explicitly differentiate from request_data.

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 implies when the tool is useful: get a free aggregate view of agent demand. However, it gives no explicit when-to-use/when-not-to-use guidance and names no alternatives, leaving routing to inference.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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

With no annotations present, the description carries the full burden and meets it: it states the operation is free, that requests are catalogued, that no identifying information is stored, and what the response will contain. This gives an agent a clear picture of side effects and privacy expectations beyond the bare schema.

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 sentences, each carrying necessary information: cost, expected outcome, and data-handling behavior. The description is front-loaded with the most actionable detail and wastes no words.

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 tool with no output schema, the description fully equips an agent: what to submit, what to expect back, cost implications, and privacy guarantees. Nothing critical is missing.

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%, so the schema already fully documents the 'need' parameter with an example. The description reinforces that the parameter can be free-form ('anything, not just URLs'), but adds no new semantic detail beyond what the schema provides. Baseline 3 is appropriate.

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 clearly states the tool's action: users describe in their own words what data they want, and the tool returns whether a service supplies it plus the MCP endpoint. It distinguishes itself from sibling tools by explicitly covering 'anything, not just URLs,' positioning it as a free-form request tool rather than a concrete URL/page/header resolver.

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 implies when to use it: when the desired data isn't easily expressed as a URL and you want to check availability before buying. It does not explicitly name sibling tools or state 'use resolve_url/site_pages/url_headers for URL-based lookups,' so some inference is required, but the 'anything, not just URLs' phrasing provides reasonable context.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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

With no annotations provided, the description fully carries the behavioral burden. It discloses the one-hop iteration behavior, the 10-hop limit, refusal to follow redirects into private address space, and the per-call cost via x402 on Base. This is far beyond minimal and gives the agent realistic expectations.

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 sentences pack the purpose, output details, usage guidance, safety limits, and cost without redundancy. The most important behavior is front-loaded, and every clause earns its place.

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 tool with no output schema and no annotations, the description is remarkably complete: it explains what the result contains, how far it will go, what it refuses to do, and what it costs. An agent has enough context to select the tool and interpret its results.

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% and the lone 'url' parameter is already described with an example. The description adds contextual color about shortened/tracked/unfamiliar links, but does not materially extend the parameter semantics beyond what the schema provides, so baseline 3 is appropriate.

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 precise operation—following a URL's redirect chain hop by hop and reporting each step—along with the specific outputs (intermediate host/status, final destination, cross-host flag, cleaned URL). This clearly distinguishes it from siblings like url_headers, which inspects headers rather than resolving redirects.

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 explicitly says to use the tool before following or showing a shortened, tracked, or unfamiliar link, and notes that a shortener cannot hide its destination. It does not explicitly name alternative tools or exclusion cases, but the use context is clear.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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

With no annotations provided, the description carries full burden and does substantial work: it discloses the lookup order (robots.txt then /sitemap.xml), how sitemap indexes are surfaced, and the per-call cost of $0.008 USDC. The cost disclosure is especially valuable behavioral context for an agent deciding whether to invoke. It stops short of describing failure behavior when no sitemap exists, a modest gap.

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?

Four sentences, each with distinct value: core function, usage guidance, edge-case index behavior, and cost. The most important information is front-loaded, and there is zero redundancy with the schema or title.

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 simple read-only enumeration tool with 2 parameters and no output schema, the description covers the essential ground: what is returned, how it is located, index handling, and pricing. The lack of an output schema raises some burden to describe return shape, which is partially addressed ('pages with last-modified dates'). Error and pagination details could round it out but are not critical.

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% for both parameters, so the baseline of 3 applies. The description adds implied meaning to the url parameter by explaining how the root URL is resolved (robots.txt first), but the limit parameter semantics are fully handled by the schema. The description does not need to compensate for any schema gap.

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 the specific resource ('pages a site declares in its sitemap'), the data included (last-modified dates), and the discovery method (robots.txt first, /sitemap.xml second). This clearly differentiates it from sibling tools like resolve_url and url_headers, which handle URL mechanics rather than content enumeration.

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?

Explicit use cases are given: enumerate a documentation set or blog archive before deciding what to read. The phrase 'instead of crawling blindly' provides an exclusion condition. The sitemap-index note ('call again for the child sitemaps') advises a follow-up action. It doesn't name sibling alternatives, but the siblings serve clearly different purposes, so the omission is minor.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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

With no annotations, the description carries the behavioral burden. It goes beyond the basic fetch by disclosing the cost per call ($0.005 USDC via x402 on Base) and adding an important interpretive caveat that header presence is a hygiene signal, not a safety verdict. This is meaningful behavioral and risk context.

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?

Four sentences, each earning its place: output inventory, use cases, safety caveat, and cost. The most important scoping information is front-loaded, and there is no redundant or filler text.

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 simple one-parameter tool with no output schema and no annotations, the description covers selection, invocation, cost, interpretation, and limitations. An agent has enough context to decide when to call it and what to expect without needing additional documentation.

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%, and the schema already documents the single 'url' parameter with examples and a clear description. The tool description adds little beyond implying the URL should be well-formed, so the baseline 3 is appropriate.

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 clearly identifies the tool's purpose by enumerating what it returns: response status, server software, content type, caching, and security headers. It implies a fetch/inspect operation on a URL without naming a sibling alternative, but the resource and output are specific enough to distinguish it from the sibling list.

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 gives explicit use cases: checking whether a URL is live and well-formed before relying on it, and cheaply profiling a site without downloading it. It does not state when not to use it or name alternative tools, so it falls short of a 5, but the context is clear.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.