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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds value by disclosing that the response includes a full field set plus a one-sentence summary and price history, which the agent could not otherwise know 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?

Two sentences, both earning their place: the first front-loads what is returned, the second gives the selection condition. No redundant restatement of the title or schema.

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 two-parameter read tool with full annotations and full schema descriptions, the definition covers the return contents and the invocation trigger. The only small gap is that it does not mention that the language parameter controls which language the returned text fields use.

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 both the id and the language parameter (with its enum and default) are already documented. The description's note that the id comes from search results duplicates the schema's own wording, and the language parameter is not mentioned, so it adds no meaning beyond the schema.

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 concrete verb and resource ("Returns one tariff in full") and enumerates the content returned: costs, data, network, speed, term, summary, price history. This differentiates it from a list/search tool by emphasizing the single, complete record, though it never names search_tariffs or list_providers explicitly.

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?

Gives a clear use condition ("when the user asks about one specific tariff") and even explains where the required id comes from (tariff search results). It lacks an explicit when-not or a named alternative, but the trigger condition is unambiguous.

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