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 description's main behavioral addition is the clarity that the active filter defaults to true and why active=true is useful. The description also specifies ordering by 'soonest end date,' which adds useful behavioral context beyond annotations. While it could mention rate limits or data freshness, the core traits are well-covered.

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 concise sentences with zero redundant words. It front-loads the core action and examples, then adds the critical usage guidance. Every sentence serves a distinct purpose.

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 the tool has no output schema, the description compensates somewhat by explaining the promotional examples and ordering. However, it doesn't clearly state that the response includes fields like promotion type, discount amount, or validity period. For a tool with 5 optional parameters and moderate complexity, slightly more detail on what the response contains would be helpful. Still, for a read-only filtered list tool, it is largely complete.

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 the baseline is 3. The description adds a usage hint linking to optimize_delivery and shows how to use active=true, but it doesn't add syntax, format, or example values beyond what the schema already provides for each parameter. The description doesn't compensate further; thus, a 3 is warranted.

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 states a specific verb ('List') and resource ('promotions'), provides concrete examples of what a promotion looks like ('2 for 30₪', club-member price, second-unit discount), and explains filtering options. This effectively distinguishes the tool from siblings like get_product or search_products, which deal with different resources.

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 tells when to use this tool: 'to explain why an optimize_delivery line price is lower than list_price.' This directly connects it to a sibling tool (optimize_delivery) and provides clear context for invocation. No other sibling seems to serve this purpose, making the guidance highly effective.

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