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

Annotations already cover the read-only, idempotent, non-destructive safety profile. The description adds value by disclosing that output includes 'period, source and license' and by explicitly scoping out asking prices, rents, valuations, and forecasts. This manages agent expectations about the returned data beyond what annotations provide.

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 deliver the core action, the exclusions, and the usage prerequisite with no filler. The most important information is front-loaded, and every sentence earns its place.

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 simple read-only lookup with no output schema, the description specifies the data source, exact metric, included metadata, and required inputs. It does not describe the exact response shape or edge-case behavior, but the annotations and simple parameter set reduce the risk of misinvocation.

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 parameter meaning. It does clarify that district and municipality are 'slugs' and both are required, which the schema does not state. However, the optional locale parameter is never mentioned, leaving its semantics entirely to the schema enum/default.

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 begins with a specific verb and resource: 'Read INE median completed dwelling sale value per m2 for a Portuguese municipality.' The explicit negatives ('Not asking prices, rents, a valuation or forecast') clearly separate this statistical tool from the property-level sibling tools.

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 clear precondition ('Requires both district and municipality slugs') and states what the tool is not for, which is a useful when-not signal. It does not name an alternative tool like search_properties for the excluded cases, so it stops short of full routing guidance.

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