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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false. The description adds valuable behavioral context: sampling frequency (5 minutes), default reading period (~1 hour), and interpretation (lower values mean cleaner electricity). It does not contradict annotations and provides meaningful extras.

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 has some redundancy: 'sampled every 5 minutes per bidding zone' and 'Lower values mean cleaner electricity' appear twice. While the information is front-loaded and clear, it could be more concise without losing meaning.

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 no output schema, the description does not explain the return format or provide an example response. The tool is simple (numeric values), so the omission is minor, but for completeness, an example or description of the response structure would be beneficial. Annotations cover safety but not return semantics.

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% with both parameters described. The description adds context beyond schema: it explains the 'area' zones (DK1=west, DK2=east) and clarifies the 'limit' default (12 readings = ~1 hour) and the meaning of values (lower is cleaner). This enhances understanding beyond the schema alone.

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 returns real-time grid CO2 emission intensity (g CO2/kWh) from Energinet Denmark, with specific sampling frequency (5 minutes), zones (DK1/DK2), and default reading count (12). It effectively distinguishes from sibling tools like spot_prices by specifying the exact data source and metric.

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 when to use this tool (for real-time CO2 intensity data) and provides context on default behavior. However, it lacks explicit guidance on when not to use it or alternatives for historical or forecast data. Given the tool's simplicity, the guidance is adequate but not comprehensive.

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