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

With no annotations, the description usefully conveys a current-data lookup and discloses the one-credit cost. However, it leaves the data source, refresh cadence, and behavior for invalid postcodes unstated.

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 front-loaded, covering purpose, scope, output content, and cost without filler. The parenthetical cost disclosure is efficient and easy to notice.

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 lookup, it provides enough information to select the tool and generally invoke it correctly. With no output schema, the lack of intensity units, source or freshness details, and precise postcode syntax are noticeable but not fundamental gaps.

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?

Although schema coverage is reported as complete, the schema's "string" description adds little; the main description connects postcode to regional intensity and implies that national results are available without it. Accepted postcode granularity or format remains undocumented.

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 precisely identifies the resource, temporal scope, geography, and included generation mix: current GB grid carbon intensity at national or postcode-region level. This clearly distinguishes it from weather and other lookup siblings.

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?

"Current" and the national-versus-postcode-region distinction give clear selection context and implicitly exclude historical or forecast lookups. It does not explicitly say to omit postcode for national results or identify any alternative tool.

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