VPN.FAIL MCP

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

No annotations are provided, so the description carries the burden. It discloses the key behavioral trait of using a random live proxy, which is valuable, but does not mention potential failures, rate limits, or handling of non-HTTP responses. It also does not explicitly confirm safety (read-only), though fetching is inherently non-destructive.

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 a single, front-loaded sentence that conveys the core action, the proxy mechanism, and the output types. Every element earns its place with no wasted 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?

Given the tool's simplicity (two parameters, one required) and the presence of an output schema, the description is largely complete. It covers what the tool does and the main output options, but could be enhanced with brief notes on proxy behavior or error outcomes to fully round out the context.

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 0%, and the description does not directly explain the 'url' or 'output' parameters. It indirectly hints at output options by listing Markdown, text, or HTML, but lacks detail on allowed values, defaults, or URL requirements, leaving the schema to carry all parameter meaning.

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 uses a specific verb ('Fetch') and clearly identifies the resource ('one HTTP(S) URL') and the output formats ('Markdown, text, or HTML'). This fully distinguishes it from the sibling tools 'service_status' and 'usage'.

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 the tool is for retrieving web content via a proxy, which gives clear context for when to use it. However, it does not explicitly state when not to use it or mention alternative tools, though the sibling set is small and distinct.

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?

No annotations are provided, so the description carries the full burden for behavioral disclosure. The verb 'Return' implies a read-only operation, but the description does not explicitly state that there are no side effects, whether authentication is needed, or whether the information is cached or real-time. This is only minimally transparent.

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 a single, front-loaded sentence that directly states the tool's purpose. Every word contributes meaning, and there is no redundancy or 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?

Given the tool has no parameters and an output schema is present, the description sufficiently covers the main return items ('proxy inventory' and 'MCP request availability'). The minimal context is acceptable for a simple status check, though it could slightly clarify what 'availability' means.

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 tool has zero parameters, and the schema confirms this. Per the rubric, a baseline of 4 is appropriate when there are no params; there is nothing for the description to add about parameter meaning.

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 uses a specific verb ('Return') and identifies the resources ('proxy inventory' and 'MCP request availability'), making the tool's function clear. It does not explicitly compare itself to siblings, but the distinct resource names and tool name differentiate it adequately from 'scrape' and 'usage'.

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 gives no guidance on when to use this tool versus the sibling tools or under what conditions it should be called. It only states what it returns, leaving the agent to infer when to invoke it.

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 full burden of behavioral disclosure. 'Return' clearly indicates a read-only operation, and 'anonymous client' implies no authentication. However, it does not mention whether this affects any counters, possible errors, or rate-limit implications. The output schema covers return structure, but additional context on side effects (if any) is missing.

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 a single, concise sentence that front-loads the action ('Return') and specifies the exact data returned. No unnecessary words or repetition; every element adds value.

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?

This is a simple tool with no parameters and an output schema, so the description is largely sufficient. It clearly states what is returned but could be enhanced with a note on typical use cases (e.g., avoiding rate limits) or a pointer to a sibling like 'service_status' for alternative needs. Given the low complexity, the minor gap is acceptable.

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 tool has zero parameters, so schema coverage is trivially 100%. The description does not need to explain parameters as there are none. Baseline for zero parameters is 4, and nothing in the description detracts from this.

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 uses a specific verb ('Return') and clearly identifies the resource ('quota usage') with time granularities ('hourly, daily, weekly, and rolling 30-day'). It distinguishes from siblings like 'scrape' and 'service_status' by focusing on usage quota rather than content or service health.

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 the tool is for checking quota usage, but it does not explicitly state when to use it or provide alternatives. Since the sibling tools exist (e.g., 'service_status'), some exclusionary or comparative guidance would improve clarity, but this is not provided.

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