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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds real behavioral context beyond that: the result set is anchored to today, it bundles penalty rules and a calendar feed alongside the date list, and start_year narrows the view rather than replacing the default output — useful for a read-only tool with 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?

The primary payload is front-loaded in the first sentence, with the start_year conditional placed last where it belongs. It is a dense enumeration, but every clause names a distinct return component, so the length is largely earned.

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 no output schema, the description carries the burden of describing returns and does so concretely (next quarterly update plus period, next SA return and payment date, upcoming list, penalty rules, calendar feed). Combined with annotations covering the read-only profile and a fully documented schema, an agent has enough to call it correctly; only the count/pagination interaction and date-relative framing are left implicit.

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 both parameters (count with its 1–12 bounds and default 6, start_year with its three-value enum) are fully documented in the schema. The description restates start_year's filtering effect but adds no detail the schema lacks, and never mentions count. 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 resource and enumerates exactly what comes back: the next quarterly update with its covered period, the next Self Assessment return and payment date, the upcoming list, current penalty rules, and a calendar feed. That content profile is clearly distinct from check_mtd or the software-lookup siblings, though it never names an alternative explicitly, which keeps it just short of a 5.

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 only guidance is conditional on a parameter: 'Give start_year to see only the dates for people who start MTD that year.' There is no statement of when to reach for this tool versus its siblings, and no exclusions or prerequisites (e.g. that it is date-relative to today). Usage is implied by the tool's nature rather than described.

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