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

Annotations already declare the tool read-only, idempotent, and non-destructive, so the description appropriately adds value beyond them by disclosing that data is collected weekly from the Médiateur national de l'énergie comparator, including the date of the last weekly reading. It also discloses the C4 limitation transparently. This is solid behavioral context without contradicting annotations.

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 efficiently structured: the first sentence front-loads the main catalog contents for C5, and the second sentence handles the C4 exception. Every clause adds distinct information, with no filler or 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 no parameters, rich annotations, and an existing output schema, the description covers the essential context: what data is available, for which segments, how current it is, and where it originates. The C4 limitation is explicitly disclosed, so an agent has enough context to invoke the tool correctly and interpret its results.

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 is empty with 100% coverage, so there is nothing for the description to explain about inputs. The description instead compensates by enumerating the output aspects, which is appropriate for a parameterless catalog tool. The baseline of 4 for zero parameters is warranted.

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 identifies the tool as a verified catalog of professional electricity offers, specifying the C5 segment and the exact data points returned (number of active offers, suppliers, price range, fixed/indexed split, date of last weekly update). It also explicitly differentiates the C4 segment behavior, making the tool's scope unmistakable and distinguishing it from the analysis-oriented 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?

The description provides clear context on what the tool returns for each segment, including the important limitation that C4 prices are only available on quote. However, it does not explicitly state when to choose this tool over sibling tools or mention alternatives by name, so it stops short of full usage direction.

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