CoinMarketCap MCP Server

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 states the tool returns historical values, implying a read-only operation, but doesn't specify data format, time range constraints, pagination behavior, rate limits, or error handling. For a tool with two parameters and no annotations, this leaves significant gaps in understanding how it behaves beyond the basic purpose.

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: 'Returns historical CMC Crypto Fear and Greed Index values.' It's front-loaded with the core purpose, has zero wasted words, and is appropriately sized for a simple tool. Every part of the sentence contributes essential information without redundancy.

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 (2 parameters, no output schema, no annotations), the description is incomplete. It states what the tool does but lacks details on parameter usage, return format, behavioral traits, or differentiation from siblings. For a data-fetching tool with undocumented inputs, this leaves the agent under-informed about how to invoke it effectively and interpret 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?

The input schema has 0% description coverage, and the tool description provides no information about the parameters 'start' and 'limit'. It doesn't explain what 'start' refers to (e.g., index, date, offset), what units 'limit' uses, or how they interact. With low schema coverage, the description fails to compensate, leaving parameters undocumented and their semantics unclear.

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: 'Returns historical CMC Crypto Fear and Greed Index values.' It specifies the verb ('returns'), resource ('historical CMC Crypto Fear and Greed Index values'), and distinguishes it from sibling tools like 'fearAndGreedLatest' by indicating historical data. However, it doesn't explicitly differentiate from other historical tools like 'cmc100IndexHistorical' beyond the specific index type.

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 alternatives. It doesn't mention when to prefer it over 'fearAndGreedLatest' for historical vs. latest data, or how it relates to other historical tools like 'cmc100IndexHistorical'. There's no context on prerequisites, exclusions, or typical use cases, leaving the agent to infer usage from the name and description alone.

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