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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false. The description adds genuinely useful behavioral context beyond annotations: 'deterministic edge compute', cost ($0.005 per call), and HTTP method (GET). There is no contradiction between the description and annotations.

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 compact and informative, with the core action front-loaded and supported categories listed efficiently. The addition of source, cost, and endpoint is useful and not wasteful. Minor redundancy exists in the 'Unit conversion:' prefix, but overall every sentence earns its place.

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 tool is simple, and the schema plus annotations provide a good baseline. However, the description does not list the exact unit symbols accepted for each category, does not describe the response format, and does not state behavior for invalid units. Since there is no output schema, a bit more return-value guidance would strengthen completeness.

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%, with each parameter (value, from, to) already documented and examples provided. The description does not add parameter-level detail, but the baseline of 3 applies because the schema already carries the semantic weight. It does not need to repeat what the schema covers.

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 states a specific verb and resource: 'Convert between units' with an explicit list of measurement categories (length, mass, volume, speed, area, data, time, pressure, energy, temperature, angle). It clearly distinguishes itself from the sibling v1_fx by omitting currency and covering physical units instead, so an agent can pick this tool without ambiguity.

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 implies usage: use this tool for unit conversions within the listed categories. However, it provides no explicit guidance about when not to use it, no mention of alternative tools, and no edge-case routing (e.g., 'for currency use v1_fx'). It is minimally adequate but leaves usage decisions to inference.

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