Point: Tangent from external point

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

Annotations already provide readOnlyHint=true, and the description adds two behavioral details: the return value is an {x, y} point and the tool raises an error when the input point is inside the circle. These go beyond the annotation and aid correct invocation, though it does not mention the two-tangent ambiguity explicitly.

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 sentences with no filler. The main action, result shape, and failure condition are front-loaded in a compact and easily parseable form.

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 complete input schema, output schema, read-only annotation, and clear error behavior described, the definition provides enough information for an agent to select and invoke the tool correctly. Nothing important is missing.

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%, so the schema already documents all five parameters clearly. The description's mention of 'external point' and 'circle' maps to from_x/from_y and circle_handle, but it adds no additional parameter-level meaning beyond the schema.

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 uses a specific verb and resource: 'Compute the tangent point on a circle from an external point.' It clearly distinguishes itself from sibling point tools like point_intersection or point_from_snap by naming the exact geometric operation and the result shape.

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 establishes the applicable case: an external point outside a circle from which a tangent is needed. It also warns when the tool is not usable ('Raises if the from-point is inside'), giving clear context. It does not explicitly name alternative sibling tools, but the use case is clear enough.

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