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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is covered externally. The description contributes the expected outputs (monthly EMI, minimum down payment, full cash needed) and a numeric sanity check, which is useful, but says nothing about edge cases, rounding/currency of results, or error behavior for out-of-range input.

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?

Three tight sentences with zero filler; the worked example makes the output concrete. It does lead with an example rather than the purpose statement, and the raw URL at the end is of marginal value to an agent, costing it a top score.

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 must convey what comes back, and it does: monthly EMI, regulatory minimum down payment, and total cash required. For a 9-parameter pure-computation tool with full schema coverage and read-only annotations, the only meaningful gap is the lack of sibling disambiguation.

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% across all 9 parameters, including the Central Bank 25-year cap and VAT notes, so the schema does the heavy lifting. The description only implicitly maps inputs through its example (price, term, rate) and adds no meaning beyond the schema, making baseline 3 appropriate.

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 concretely what it computes: the Dubai mortgage EMI, the UAE Central Bank minimum down payment, and the total cash required, all anchored by a worked example (AED 1.6M / 25 years / 4.25% -> AED 8,667.81). The 'Dubai'/Central-Bank framing implicitly separates it from generic mortgage_calculator and canadian_mortgage_calculator, but it never names those siblings, so an agent must infer the boundary.

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?

There is no explicit when-to-use, when-not-to-use, or alternative-tool guidance, despite many overlapping siblings (mortgage_calculator, down_payment_calculator, dld_fee_calculator, loan_to_value_calculator). A caller has to infer applicability purely from the word 'Dubai' in the description and the tool name.

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