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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds the valuable part — the exact composition of the result (material and labour per line, preliminaries, contingency, VAT, total, likely range in rand) and the currency. It doesn't say how contingency/preliminaries actually feed the total, but this is well above the annotation baseline.

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 dense sentences, input contract first and return contract second, with zero filler. Every clause carries information an agent needs to invoke or interpret the call.

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's return breakdown does real work and covers the tool's complexity well; the input side is mostly covered by schema defaults. The remaining gap is the sibling-estimator distinction and the meaning of the percentage parameters.

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 coverage is only 33%, so description should compensate more than it does. It clarifies region (South African) and quality level and ties VAT into the output, but says nothing about contingency_pct or how preliminaries_pct interacts with the returned preliminaries line; region ids and item code format remain unelaborated.

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 (prices) and resource (list of building/renovation items) plus the geography (South African region) and quality level. It names list_cost_items as the code source, but doesn't distinguish itself from sibling estimate_new_build or roof_replacement_estimate, so an agent can't tell from the description alone which estimator applies.

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?

Implies usage via the 'by code from list_cost_items' prerequisite, which usefully signals the lookup-then-estimate flow. But there's no explicit when-to-use/when-not versus estimate_new_build or roof_replacement_estimate, leaving the most consequential routing decision to inference.

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