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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety behavior is covered. The description adds only the unit-selection note and says nothing about practical constraints an agent would hit — e.g. asin/acos domain limits, tan undefined at 90°, or whether inverse functions return in the chosen unit — which are the real failure modes for this 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?

Two short sentences with the function list front-loaded; nothing is bloated. The second sentence largely duplicates the schema's angle_unit field, which is a small redundancy rather than a real cost.

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?

With a 100% documented schema and an output schema present, an agent has everything needed to call this correctly. Only domain/precondition caveats for inverse functions are missing, which is a minor gap for a simple math tool.

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% and the schema already documents value as angle-vs-ratio and angle_unit with its default, so the schema carries the semantics. The description's 'Set angle_unit to degrees or radians' restates the enum rather than adding interpretation, so baseline 3 applies.

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 names the exact operation set (sin, cos, tan, asin, acos, atan) on a clear resource, so an agent knows this is the trig-function tool rather than the triangle/right-triangle geometry tools. It stops short of contrasting itself with those siblings by 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?

'Use this for sin, cos, tan, asin, acos, atan' gives positive selection guidance, and the angle_unit sentence hints at setup. There is no when-not guidance and no explicit routing away from calculator_right_triangle or calculator_scientific, so usage is implied rather than fully specified.

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