MCP URL Fetcher

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It mentions fetching and converting to JSON but fails to describe critical behaviors such as error handling (e.g., for non-JSON content), authentication needs, rate limits, or what happens if the URL is inaccessible. This leaves significant gaps for a tool that interacts with external resources.

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, efficient sentence that front-loads the core functionality ('fetch content from any URL') and adds the key detail ('convert to JSON format') without any wasted words. It is appropriately sized for the tool's scope.

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 complexity (fetching from external URLs with potential for errors) and the absence of both annotations and an output schema, the description is insufficient. It doesn't explain return values, error cases, or behavioral nuances, making it incomplete for safe and effective use by an AI agent.

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 has 100% description coverage, clearly documenting both parameters (url and prettyPrint). The description adds no additional semantic meaning beyond what the schema provides, such as examples or constraints. With high schema coverage, the baseline score of 3 is appropriate, as the description doesn't compensate but also doesn't detract.

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 purpose with a specific verb ('fetch') and resource ('content from any URL'), and specifies the output format ('convert to JSON format'). However, it doesn't explicitly differentiate from sibling tools like 'fetch-html' or 'fetch-markdown' beyond the JSON output mention, which is implied but not directly contrasted.

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 provides no guidance on when to use this tool versus its siblings (fetch, fetch-html, fetch-markdown, fetch-text). It lacks explicit context about alternatives, prerequisites, or exclusions, leaving the agent to infer usage based solely on the output format.

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