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

The description supplements the annotations (readOnlyHint) with key behavioral details: experimental beta status, free usage, coverage signal nature, sorting by asking_sample_n, and diacritic-insensitive search. No contradictions with annotations.

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 but front-loads the beta warning and purpose. Every sentence adds value, though some phrasing could be tightened. It remains clear without unnecessary verbiage.

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?

Given no output schema, the description explains the return type (coverage signal with sample size and confidence), sorting, and cost. It covers enough for an agent to understand what the tool provides and how to use its output with get_price_spread.

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?

The schema covers the parameter fully (100% coverage), so baseline is 3. The description adds value by restating the min length and search behavior, and providing a concrete example ('gda' → Gdańsk). This slightly exceeds the baseline.

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 identifies the tool's function: listing cities/counties for which get_price_spread can return data. It explicitly distinguishes itself from get_price_spread ('does not compute the spread') and helps the agent understand its role as a discovery tool for valid location parameters.

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 states when to use this tool ('use this to discover valid location/teryt values for get_price_spread') and when not to ('it does not compute the spread'). It directly names the alternative (get_price_spread) and explains the optional search filter, providing clear guidance.

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