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

Annotations already declare readOnlyHint, openWorldHint=false, and idempotentHint, so safety is covered. The description adds value beyond them by showing a concrete worked result ("10 km in 50 minutes is 5:00 per km or 8:03 per mile"), which reveals the dual-unit output format that no structured field provides. It stops short of disclosing the two-mode behavior.

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 worked example is front-loaded and immediately grounds the tool's purpose, followed by a compact scope sentence and a reference URL. All three sentences carry weight with no padding.

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 no output schema and 10 parameters spanning two calculation modes, the description never explains how mode toggles between pace calculation and finish-time calculation, nor how preset vs custom distance interact. The schema descriptions carry that burden, leaving the prose merely adequate for a tool of this complexity.

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 10 parameters, making 3 the baseline. The description's example loosely illustrates pace/speed output but adds no syntax or meaning beyond the schema for the mode, preset, distUnit, or paceUnit enums.

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 a specific verb+resource ("Get running pace and speed from any distance and time, or your finish time for a 5K to a marathon") and scopes it to running pace, which is clearer than a generic calculator. It does not, however, differentiate itself from the closely overlapping sibling speed_distance_time_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?

Two usage contexts are implied (derive pace from distance+time, or derive finish time from a target pace), but there is no explicit when-to-use/when-not framing and no named alternative. The agent must infer from the prose which case applies.

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