isone_fuel_mix

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

The description states it shows 'real-time megawatt output by fuel category', adding specificity beyond the readOnlyHint annotation by explaining the data granularity and temporal nature (real-time). While annotations already indicate a safe read operation, the description provides useful context about what data is returned without needing to explain return structure since there is no output schema.

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 concise (two sentences) yet information-dense, front-loading the action ('Get current ISO New England generation fuel mix') and immediately providing detail on the breakdown by fuel type. Every sentence earns its place without redundancy.

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 the zero-parameter, read-only nature of the tool and rich sibling context (e.g., presence of isone_load in siblings), the description adequately covers what the tool does, the data it returns, and the region. It doesn't explain the response format, but with no output schema and a simple data view, this is acceptable. Slight gap: no note on update frequency or data source reliability.

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 tool has zero parameters, and the schema coverage is 100% (no params). With no parameters, the schema requires no explanation, and the description provides full context by detailing what data the tool returns. The description compensates fully for the empty schema by explaining the data content.

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 clearly states the tool retrieves the current ISO New England generation fuel mix, listing specific fuel types (natural gas, nuclear, hydro, wind, etc.) and specifying the region (New England). This verb+resource+scope construction distinguishes it from siblings like isone_load and ercot_grid_conditions.

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 clearly indicates this is for current/realtime fuel mix data for New England, which implicitly differentiates it from similar tools like ercot_grid_conditions (Texas) or isone_load. However, it doesn't explicitly state when to avoid this tool or name alternatives, reserving full guidance.

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