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

Annotations already declare readOnlyHint=true, idempotentHint=true and openWorldHint=false, so safety profile is covered. The description adds that each result comes 'with its working', which is useful context about output format, but doesn't cover rounding, constraints, or error behavior. With annotations present, a 3 is fair.

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?

A single dense sentence front-loads 'Two points in, the whole line out' and then enumerates outputs efficiently. Slightly overloaded with seven output forms plus a URL, but no filler or repetition.

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?

The description enumerates all outputs so the agent knows what comes back even without an output schema, and annotations cover the safety profile. Minor gap: no note on numeric limits or how degenerate cases (e.g., vertical line where x1=x2, undefined slope) are handled.

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 coverage is 100% and each of the four parameters (x1, x2, y1, y2) is documented with symbols and numeric range. The description adds no parameter-level detail beyond noting they are two points. Baseline 3 applies when the schema carries the load.

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?

States a specific verb-like action (compute the whole line from two points) and enumerates the concrete outputs: slope fraction, y=mx+b, point-slope, standard form, angle, distance, midpoint. This is clearly distinguishable from siblings like circle_calculator or pythagorean_theorem_calculator.

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?

Implicit usage is clear from 'Two points in', telling the agent what inputs are needed, but there is no explicit when-to-use vs alternatives guidance or exclusions. In a catalog of 150+ calculators, no cross-referencing to related tools like pythagorean_theorem_calculator (which also uses two points) or triangle_calculator.

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