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

With no annotations, the description carries full burden. It discloses the ranking order (greenest first), the weighting formula (60% renewables, 40% carbon intensity), and the label boundaries, adding meaningful behavioral context beyond a simple comparison.

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 four sentences long, each earning its place: action and ranking, formula, labels, and usage guidance. 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?

For a simple one-parameter tool with no output schema, the description covers the operation, the ranking behavior, the score range, the formula, and the intended usage. It is complete enough for an agent to select and invoke correctly.

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?

The schema description for 'zones' already provides full details (comma-separated codes, example, max 10 zones). The tool description adds no extra parameter semantics, so the baseline of 3 for high schema coverage (100%) 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 states 'Compare green scores (0-100) across multiple zones in one call, ranked greenest first,' which specifies the verb (compare), resource (green scores), and scope (multiple zones). It distinguishes itself from siblings like compare_carbon and compare_prices by focusing on the composite green score.

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?

Explicitly states 'Use when the user wants to find the greenest grid for scheduling workloads,' providing clear context. However, it does not name alternative tools or give 'when not to use' guidance, so it doesn't fully meet the 5 threshold.

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