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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds domain semantics (income counted before expenses) but says nothing about what the determination returns — a boolean, a date, a threshold comparison — which matters since there is 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?

Two tight sentences, front-loaded with the determination being made before the qualifying-income rule. Every clause carries information the agent needs and nothing is repeated from the title or schema.

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?

For a two-parameter read-only check with no output schema, the description supplies the essential rule for producing a correct answer (what counts toward qualifying income). The main gap is the absence of any hint about the output form or applicable thresholds, though the annotation set covers safety concerns.

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 0%, so the description must carry the load, and it does: it defines qualifying income as self-employment turnover plus property income, before expenses, and states what is excluded. It does not clarify that propertyIncome defaults to 0, nor units/currency, but the meaning of both parameters is substantially conveyed.

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 ('say whether and when') and a precise resource (Making Tax Digital for Income Tax applicability), plus the basis for the determination (qualifying income). This distinguishes it cleanly from siblings like get_mtd_deadlines (dates) and estimate_self_employed_tax (tax estimate) 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?

The description gives clear context for invoking it (anyone whose MTD status must be determined from qualifying income) and rules out misuse by stating employment and pension income do not count. It does not, however, route the agent explicitly to alternatives such as get_mtd_deadlines or prepare_quarterly_update when those are the better fit.

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