Apollo Proxy MCP Server

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

With no annotations provided, the description carries full burden and does an excellent job disclosing key behavioral traits: cost ($0.005/request), max response size (250KB), rate limits (100 req/min), and capabilities (supports 190+ countries, rotating/sticky sessions, handles anti-bot protection). It doesn't mention error handling or response format details.

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 perfectly sized and front-loaded, starting with the core purpose, then listing key capabilities, and ending with operational constraints. Every sentence earns its place with zero wasted words, making it highly efficient for agent comprehension.

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 tool with no annotations and no output schema, the description provides excellent coverage of behavioral aspects (cost, limits, capabilities). However, without an output schema, it doesn't describe what the tool returns (response format, error structure), leaving a gap in complete understanding of the tool's interface.

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%, providing comprehensive parameter documentation. The description adds minimal parameter semantics beyond the schema, only implying the URL parameter through 'fetch any URL' and mentioning country support. Baseline score of 3 is appropriate when schema does the heavy lifting.

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 specific verbs ('fetch any URL') and resources ('through Apollo's residential proxy network'), distinguishing it from sibling tools like list_countries and proxy_status which likely provide metadata rather than performing actual fetching operations.

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 clear context about when to use this tool (fetching URLs through proxy with specific capabilities), but doesn't explicitly state when NOT to use it or mention alternatives to this tool. It distinguishes from siblings by function but lacks explicit exclusion guidance.

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