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

Annotations already declare readOnly, idempotent, non-destructive, so the safety profile is covered. The description adds non-obvious behavior beyond that: same-currency spreads are computed values, currencies are deliberately not converted, and prices are dated snapshots rather than live quotes. It stops short of describing the response shape or snapshot freshness/staleness, but the added constraints are substantive.

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?

Front-loaded with Purpose, then Guidelines, Limits, examples and a scoped summary; each section is one or two clauses and earns its place. It is on the long side for a zero-required-parameter tool, and the repeated 'same currency' constraint appears twice, but there is no filler.

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?

An output schema exists, so return structure needn't be explained. Given a two-optional-parameter, read-only comparison tool, the description covers scope, trigger conditions, the FX limitation, and the sibling alternative - everything an agent needs to select and invoke it 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% with enum values and defaults documented for both parameters, so the schema carries the semantics. The description only supplies example invocations (compare_carbon_prices(language='en')), which shows usage but adds no meaning about what language or response_format actually control. Baseline 3 applies.

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 specific verb and resource ('put every carbon price snapshot side by side') and enumerates the compared dimensions (market/basis, value, unit, date, source, spread). It explicitly distinguishes itself from the sibling get_carbon_market_overview by labeling its scope as 'SIDE-BY-SIDE comparison only', so an agent can route without opening either schema.

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 concrete triggering questions ('how do EU and China carbon prices compare', 'what is the spread between auction and secondary prices') and names the alternative tool with the condition that selects it. It also states exclusions - no cross-currency difference because no FX rate exists - so when-not-to-expect-output is explicit.

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