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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds genuinely new behavior: the output is a card with a button that opens TapTax, filing is out-of-band, and HMRC receives device details from the filing device. This goes well beyond the structured fields, though it doesn't discuss auth or rate limits.

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, front-loaded with the core purpose followed by the filing constraint. Every clause earns its place, though the second sentence is dense and could be trimmed slightly.

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 return-shape burden and does so by naming the figures returned and the card/button artifact. Combined with the filing-location disclosure, an agent has what it needs, leaving only minor gaps around permissions or freshness of the data.

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 quarter and taxYear are fully documented in the schema (quarter maps to 5 July/5 Oct/5 Jan/5 Apr, taxYear defaults to current). The description's mention of '6 April to the end of the quarter' loosely reinforces the period semantics but adds no syntax or format detail beyond the schema, so the 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+resource ('Get the signed-in person's Making Tax Digital quarterly update ready') and then enumerates exactly what it produces: cumulative income, expenses, profit for the period, review items, and a TapTax card. This clearly separates it from siblings like check_mtd_status or get_mtd_deadlines, which report status/deadlines rather than assembling an update.

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 establishes a clear boundary — it prepares the update but filing 'always happens in the TapTax app, never from the chat' — which tells the agent not to expect to file. It lacks explicit routing guidance against alternatives (e.g. when to prefer check_mtd_status), so it is clear context without named exclusions.

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