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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds essentially nothing beyond that — no note on behavior when an ID is not found, no indication of what the response contains, and 'via DiscountHub API' is filler rather than behavioral context.

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?

A single front-loaded sentence with no padding; the resource and the exact-ID constraint come first. The trailing 'via DiscountHub API' is mildly redundant but costs almost nothing.

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 two-parameter read tool with no output schema and no per-parameter schema descriptions, the description covers the core lookup intent but omits return shape, not-found behavior, and the allowed kind values. Minimum viable, with clear gaps an agent would otherwise have to discover by trial.

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% for two required parameters, so the description must compensate. It partially does: 'deal or promotion' maps to the kind parameter (schema constrains it to deals|promotions) and 'exact ID' clarifies that offer_id is a precise match, not a partial search. However, it never states the valid kind values or the ID format/length constraint.

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 (look up) and resource (a deal or promotion) with the key scoping qualifier 'by its exact ID,' which distinguishes it from fuzzy siblings like search_deals. It stops short of explicitly naming which sibling to use instead, so it is clear but not fully differentiated.

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 phrase 'by its exact ID' implies this is the tool to use when a precise identifier is already known, but there is no explicit when-to-use/when-not guidance and no alternative named (e.g., search_deals for name-based lookup). Usage must be inferred.

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