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

With no annotations, the description carries the full burden and does disclose two critical behaviors: paid access at $0.005 USDC per call via x402 payment metadata, and a free sample=true path capped at 3 rows. That is exactly the kind of cost/precondition context an agent needs before invoking. It does not cover error behavior, rate limits, or auth failure modes, keeping it short of a 5.

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?

Dense and front-loaded: identity, routes, pricing, and the free-preview escape hatch all arrive in a compact block. The middle clause listing target audiences ('energy apps, climate tools, maps, simulations, city-building games and AI agents') is pure filler that earns no place for an agent consumer.

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 nested multi-route gateway with no output schema, the description supplies the route inventory, per-route parameters, and payment mechanics — enough to call it correctly. What's missing is any sense of the response shape or the meaning of edge syntax like the 'lat*' marker, but those are secondary for a lookup tool.

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%, so the baseline is 3, but the description adds real value by mapping which parameters belong to which route (lat*, lon*, fuel, min_mw, limit for /nearby; q, country, fuel, min_mw, limit, offset for /search) — information absent from the generic 'params' object schema. The unexplained asterisk on 'lat*' and the absence of units on min_mw are minor gaps.

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 resource (global power plant data) and enumerates the five concrete routes, so the agent knows the tool's actual capability surface. It doesn't need to differentiate against siblings like 'airports' or 'exchanges' since the domain is self-evident, but the opening tagline ('Power Plants of the World') is branding rather than a verb+resource statement.

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 audience list (energy apps, climate tools, games) hints at use cases, and the route enumeration implies what each sub-query does, but there is no explicit guidance on when to pick /nearby over /search, and no when-not-to-use or prerequisite statement. An agent must infer route selection from parameter names alone.

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