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

Goes well beyond the readOnly/idempotent annotations by disclosing dual response modes (native render in MCP Apps clients vs. data + map link elsewhere) and the edge case where an ambiguous postal code returns an 'options' field. Data provenance and vintage (RPG 2025, BNVD 2024, SISE-Eaux 2025) are also stated, which matters for trusting the result.

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?

Purpose is front-loaded, but the identifier paragraph partially restates the schema's own resolution rule and examples, and the source/licensing block is a long trailing list of dataset versions. Licensing attribution is defensible, yet roughly a third of the text is provenance rather than invocation guidance.

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 carries the return-value burden and does so: it says the response either renders a map or contains data plus a map link, and flags the 'options' field for ambiguous postal codes. What the returned data actually contains (parcel attributes, halo geometry) is left unspecified.

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 baseline is 3, but the description adds real value: it explains the resolution precedence for 5-digit codes with a concrete collision example (59175 = Templemars CP vs. Dimont INSEE) and the fallback 'options' payload for shared postal codes. This is meaningfully more than the schema's brief 'INSEE en priorité' note.

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 and resource: an interactive map of agricultural parcels within a 1 km halo of a commune, including 'bio' parcels. It is unmistakably the visualization tool among siblings that return data (get_commune_exposure, rank_communes), though no sibling is named explicitly.

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?

Usage is implied (you want a visual map of parcels around one commune), and it explains rendering behavior across client types, but there is no explicit when-to-use/when-not guidance relative to search_communes or get_commune_exposure. The agent must infer that this is the 'render' tool rather than the 'query' tool.

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