unit_conversion_radiansToLength

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

With no annotations provided, the description carries the full burden of behavioral disclosure and does so well. It explains the calculation method ('基于地球半径计算地面距离', '转换公式: 距离 = 弧度 × 地球半径'), dependencies ('依赖于 Turf.js 库和 Node.js 环境'), error conditions ('当 JavaScript 执行失败、超时或输入数据格式错误时抛出异常'), and return format. It doesn't mention rate limits or authentication needs, but those seem unnecessary for this type of calculation tool.

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 well-structured with clear sections (Args, Returns, Raises, Example, Notes) and front-loads the core purpose. However, it includes some redundant information like the Python import example which may not be necessary for an MCP tool description, and the Notes section could be more concise. Overall efficient but with minor verbosity.

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 2-parameter calculation tool with no annotations and no output schema, the description provides complete context. It explains the tool's purpose, parameters, return format, error conditions, calculation method, dependencies, and includes a practical example. The description fully compensates for the lack of structured metadata, making the tool's behavior and usage clear.

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?

With 0% schema description coverage, the description fully compensates by providing comprehensive parameter documentation. It clearly explains both parameters: 'radians' as the radian value to convert with type, description, and example, and 'units' as the output distance unit with type, description, valid values, default, and example. This adds significant value beyond the bare schema which only shows types and default.

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: converting radian distances to ground lengths based on Earth's radius. It specifies the verb ('将弧度距离转换为长度' - converts radian distances to lengths) and resource (radian values to length values), distinguishing it from sibling tools like unit_conversion_degreesToRadians or unit_conversion_convertLength by focusing specifically on radian-to-length conversion with Earth radius calculation.

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 for when to use this tool: for spherical geometry calculations where radian distances need to be converted to ground distances. It mentions being '常用于球面几何计算' (commonly used in spherical geometry calculations). However, it doesn't explicitly state when NOT to use it or name specific alternatives among the many sibling tools, though the context implies it's for radian-based conversions specifically.

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