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

Annotations already mark the tool as read-only, idempotent, and non-destructive. The description adds meaningful behavior beyond that: it explicitly handles edge cases rather than returning nothing, treats foreign property as a separate business, notes there is no key, says attribution is required, and cites traceable sources plus the governing regulation. No contradiction with annotations.

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 description is front-loaded with the core one-call framing and outputs, but the first sentence is a long, run-on enumeration. The closing sentences about sourcing and the governing regulation are relevant for trust and attribution but are slightly tangential to calling the tool; overall it's dense but not bloated.

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 does the needed work by enumerating what the caller gets: in/out status, scope date, threshold, deciding tax return, quarterly deadlines and count, exemptions, and special cases. It also communicates service constraints (free, no key, attribution required, sourced facts), making it sufficient for an agent to invoke the tool without major unknowns.

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?

The input schema already documents all five parameters at 100% coverage, so the baseline is 3. The description reinforces the meaning of qualifying income and warns that foreign property is separate, but most of that is already present in the schema's property descriptions, so the description adds little beyond the structured documentation.

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?

The description opens with a clear 'One call for UK Making Tax Digital for Income Tax scope' and specifies exact inputs and outputs (income, in/out status, date, threshold, tax return, deadlines, exemptions). It is unambiguous and domain-specific, but it does not explicitly contrast the sibling tools like get_mtd_answer or search_mtd_answers, so it stops short of full differentiation.

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 gives a strong contextual sense that this is the purpose-built tool for MTD scope: yielding income as input and returning scope details, including automatic exemption and 'not-yet-but-soon' cases. However, it never names alternatives or conditions for when NOT to use this tool, so usage guidance is clear by context but not fully explicit.

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