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

Annotations already declare readOnly/idempotent/non-destructive/openWorld=false, so the safety profile is covered. The description adds real behavioral context: it is timeline-only, dates are sourced from cited documents and 'not forecasts', and the phase grouping is the tool's own rather than the EU's official staging. These caveats are exactly the kind of disclosure annotations cannot express.

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 and labelled (Purpose / Guidelines / Limits / Ex), so an agent can skim to the relevant section. It is somewhat dense, with the Limits block slightly overlapping the grouping explanation already implied in Purpose, but every sentence carries useful 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?

With an output schema present, return-value explanation is unnecessary, and the description still covers purpose, trigger conditions, phase grouping logic, sourcing caveats and a companion tool. Nothing an agent needs to call it correctly is missing.

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% and both enum params (language, response_format) are documented in-schema, so the baseline is 3. The description only adds invocation examples (get_cbam_timeline(language='en')) and does not explain defaults or format tradeoffs beyond what the schema states.

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 resource and scope: 'the CBAM timeline as a single ordered view' spanning the founding regulation, transitional period, definitive regime and surrender phase. The CBAM specificity clearly separates it from other timeline siblings such as get_battery_regulation_timeline or get_telecom_policy_timeline without needing to name them.

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?

Explicitly says 'call this first whenever a question involves CBAM dates, obligations or scope' and supplies trigger phrases ('when does CBAM start', 'when must certificates be surrendered'). It also names a downstream pairing, get_domain_benchmark(id=...), for source URLs, which is genuine when-to-use routing.

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