acos

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

No annotations are provided, so the description carries full burden. It mentions the output unit (radians) but lacks critical behavioral details: input constraints (e.g., value range -1 to 1), error handling for invalid inputs, precision/rounding behavior, or whether it handles complex numbers. For a mathematical function with no annotation coverage, this is a significant gap.

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 extremely concise (one phrase) and front-loaded with the core purpose. Every word earns its place: '计算反余弦值' defines the operation, and '（返回弧度）' adds crucial output unit information. No wasted words or redundant structure.

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 no annotations, no output schema, and 0% schema description coverage, the description is incomplete. It covers the basic operation and output units but misses input constraints, error conditions, precision details, and mathematical context needed for reliable use. For a mathematical function with behavioral nuances, this leaves too many gaps.

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%, so the description must compensate. It adds no parameter semantics beyond the schema's generic 'value' parameter. The description doesn't explain what 'value' represents (e.g., cosine value between -1 and 1), its expected format, or units. With 1 undocumented parameter, the description fails to provide meaningful context.

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: '计算反余弦值（返回弧度）' translates to 'calculate arccosine (returns radians)'. It specifies both the mathematical operation (arccosine) and the output unit (radians), which distinguishes it from potential degree-based alternatives. However, it doesn't explicitly differentiate from sibling tools like 'asin' or 'atan' beyond the mathematical function name.

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 the input domain (e.g., value must be between -1 and 1 for real arccosine), nor does it reference sibling tools like 'acos' vs 'acosh' (inverse hyperbolic cosine) or 'radToDeg' for unit conversion. Usage is implied by the mathematical function name alone.

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