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

Annotations already declare readOnlyHint=true and openWorldHint=false, and the description adds substantial value beyond that: a 15-credit cost, the fact that it returns structured JSON rather than an image, and the conditional MCP-Apps interactive-map rendering behavior. It also discloses the scope-filter requirement and default date window.

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?

Front-loaded with purpose, then grouped bullets for required/optional/returns, then when-to-use, then an example. Well structured and mostly tight, though the 'not a rendered map or image' caveat is repeated in two places and could be stated once.

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?

No output schema exists, but the description compensates fully by enumerating the per-zone return fields (centroids, median/avg price/m², transaction count, relative position label), and it covers cost, defaults, and the scope-filter constraint. An agent has everything needed to call it correctly.

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%, so baseline is 3, but the description adds real meaning the schema does not encode: the schema lists no required parameters, yet the description states at least one scope filter (code_departement or commune) is REQUIRED, plus the 'returns all arrondissements' behavior for commune. It adds little beyond the schema for group_by/type_local/min_transactions.

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?

Starts with a specific verb+resource ('Get price statistics aggregated by postal code or commune zones') and immediately disambiguates from a rendered-map tool. The sibling set contains several analysis tools, and the description's emphasis on zonal aggregation vs. whole-market statistics makes the boundary reasonably 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?

Provides an explicit 'Use this when you need to' block with three concrete scenarios plus a 'Do NOT call this expecting a rendered image' exclusion. It stops short of naming a specific sibling alternative (e.g., compare_locations or analyze_market_statistics) for the cases where a non-zonal comparison is wanted.

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