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

With no annotations provided, the description carries the burden of disclosure. It states that location-based emissions are always returned and market-based only when specific inputs are supplied, and mentions that supplier_factor wins over market_factor_key (via schema, not description). It does not describe the output format or error handling, but for a calculation tool, the core behavior is adequately transparent.

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 two sentences, front-loaded with the tool's purpose, and every clause adds value. It is compact and well-structured, with no redundant information.

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 tool's moderate complexity (two methods, two optional parameters) and 100% schema coverage, the description covers the main usage scenarios well, including how to obtain factor keys. It lacks mention of the output structure or precedence between supplier_factor and market_factor_key (though schema covers precedence), but overall it is sufficiently complete for an agent to invoke correctly.

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 description coverage is 100%, so baseline is 3. The description adds context beyond the schema: it explains the role of supplier_factor (e.g., green tariff/REC = 0) and market_factor_key (residual mix), and directs to search_factors for keys. This extra context justifies a 4.

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 it calculates GHG Protocol Scope 2 for purchased electricity using both location-based and market-based methods, distinguishes from sibling calculation tools by specifying the resource (electricity) and the dual-method scope, and mentions referencing search_factors for grid keys.

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?

It explicitly explains when to use market-based (supplying supplier_factor or market_factor_key) versus location-based (always returned) and points to search_factors for key discovery. However, it does not directly compare with other calculation tools or state when not to use this tool, though the scope is well-defined.

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