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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and non-destructive, so the safety bar is low. The description adds real context beyond them: monthly cadence, MWh units, and the default national rollup, which the agent could not infer from the annotations alone.

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 tight, front-loaded sentences that each convey something: what it returns, the dimensionality (source), and the optional filter. The source enumeration duplicates the schema enum, slightly redundant but not wasteful.

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 read-only query tool with full schema coverage, strong annotations, and no output schema, the description covers resource, cadence, dimensions, default, and unit. Minor gaps (pagination/limit behavior) are handled by the schema.

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. The description restates the source list and the state default, both already fully documented in the schema, and adds no new meaning (e.g., valid date formats for start/end or limit semantics).

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 verb+resource: 'Monthly US electricity generation by source from EIA,' plus the return unit (megawatt-hours). It is clearly distinguishable from generic EIA tools, though it never explicitly names a sibling (e.g., eia_electricity_state) to sharpen routing.

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 notes the state filter is 'optional (default national),' which implies usage scope, but it gives no explicit when-to-use/when-not guidance and does not contrast with the many neighboring EIA tools (eia_electricity_state, eia_series_lookup).

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