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

Annotations already declare readOnlyHint=true, so the description adds extra behavioral context beyond annotations by disclosing 'Updates: daily', the output components (score, trend, confidence, top_drivers), and the data sources (POS volume, discount depth, promo calendars, competitor pricing). No contradiction exists.

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 two tightly structured sentences. The first sentence defines the output and calculation inputs; the second provides actionable use cases. It is front-loaded with the core return value and contains no unnecessary words.

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 no output schema, the description lists the return components and update frequency. It covers purpose, usage, and (with the schema) parameter behavior. Minor omissions like score direction and explicit mention of optional history mode are not critical since the schema covers that.

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 input schema provides 100% coverage for the single optional 'days' parameter, including the Gold tier requirement for history. The description itself adds no parameter-specific meaning, so the baseline score of 3 is appropriate.

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 uses a specific verb 'Returns' and identifies a precise resource: '0-100 promo-elasticity gap score by retail category'. It further explains the metric's construction (realized ROI vs elasticity-implied maximum) and data inputs, making the tool's function unambiguous and distinguishing it from other analytics 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 explicitly lists when to call the tool: 'when the user asks about promotion effectiveness, trade-spend ROI, discount depth, or price elasticity, or when timing trade-budget reallocation and promo-calendar decisions.' This is clear context, but it does not mention alternatives or exclusions, so it stops short of a full 5.

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