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

With no annotations, the description carries the full burden. It discloses that returns are in cents and formatted in euros, and that it includes the source of the tables, which is useful. However, it does not reveal the actual return structure (e.g., whether it returns an object with breakdown or just a total) or any assumptions beyond 'primary_home' and 'buyer_is_young'. The mention of official tables adds credibility but lacks detail on edge cases (e.g., what happens for non-first-home purchases).

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 concise and front-loaded with the key purpose, then adds relevant detail about the tables and young buyer discount. It is a single sentence that covers scope, inputs, and outputs without redundancy. The only minor inefficiency is the phrase 'what buying a home in Portugal costs on top of the price' which is slightly wordy but useful.

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 tool with 4 parameters, high schema coverage, and no output schema, the description is reasonably complete. It explains the purpose, the inputs (via context), the outputs (cents and euros, source), and identifies the key variant (young buyer scale). It could be improved by explicitly stating how the result is structured (e.g., a breakdown) and any limitations (e.g., does not include other taxes), but for the complexity level, it is adequate.

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 100%, so the schema already describes each parameter. The description adds the value of mentioning the reduced scale for young buyers, which maps to the 'buyer_is_young' parameter, and confirms 'primary_home' is for habitação própria. However, it does not add format details beyond the schema (e.g., how to represent property value with decimals) nor clarify the interaction between 'primary_home' and 'buyer_is_young' beyond what is in the schema.

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 clearly states the tool calculates the extra costs of buying a home in Portugal, specifically listing IMT, stamp duty, and deed/registration costs. It also distinguishes itself from sibling tools by mentioning official 2026 tables and the reduced scale for young buyers, making its purpose and scope immediately clear.

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 implies this tool is used for upfront purchase costs (IMT, stamp duty, deed) versus the sibling tools like imi_annual_cost (annual property tax) and imi_rate (tax rates). However, it does not explicitly state when to use this tool over the alternatives, nor does it mention any exclusions, such as not including notary fees or other taxes.

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