compare_sites

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

With no annotations, the description carries the full burden. It discloses the internal execution ('Runs screen_site on each point'), the ranking methodology, the transparent heuristic reasoning output, and the 'No API key' authentication requirement. This adds meaningful behavioral context beyond the schema, though it could mention potential latency, error conditions, or exact output format.

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?

Three sentences with precise information: action, input range, method, criteria, output, supported regions, and authentication. No filler or redundancy. The most important info (comparison/ranking) is front-loaded.

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?

Given moderate complexity and no output schema, the description adequately covers purpose, process, and output nature. It could improve by specifying the structure of the ranking result or notable side effects, but overall it's sufficiently complete for an agent to decide invocation.

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 already provides 100% coverage of all four parameters with detailed descriptions. The tool description adds the constraint '2-10' (also present in schema) and mentions ranking criteria, but it doesn't deepen parameter understanding beyond schema. The high schema coverage makes a baseline 3 appropriate.

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 specific verbs ('Compare and rank') and a clear resource ('2-10 candidate PV/BESS sites'), then details the ranking criteria (verdict, solar resource, grid proximity, terrain). It distinguishes itself from sibling tools by explicitly noting it 'Runs screen_site on each point,' establishing itself as a multi-site aggregation tool.

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?

Clear context is provided: use for 2-10 candidate sites, supported regions (GB and EU member states), and no API key required. It also implies a multi-site comparison use case by referencing screen_site as a sub-step, but it does not explicitly state when not to use it or name alternative tools (e.g., screen_site for single-site screening).

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