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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive behavior. The description adds valuable context: data is 'freshness-stamped' and costs 1 credit with no charge if no data is returned. This goes beyond the annotations without contradicting them.

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 no fluff. It front-loads the core purpose and then adds brief, relevant billing/freshness details. 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?

The description covers enough for a single-parameter tool: what is returned (fields), cost, and freshness. The lack of an output schema is partially mitigated by listing fields, but error handling, pagination, or edge-case behavior are not mentioned. Still adequate for most agents.

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 fully documents the only parameter 'domain' as 'eCommerce domain' (100% coverage). The description complements this by linking it to 'a brand', clarifying how the parameter is interpreted. This adds semantic value beyond the schema alone.

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 the tool retrieves active promotions/discount codes for a brand, listing specific fields (code, discount type/value, min order, validity window). This is a specific verb-resource pairing that naturally distinguishes it from sibling tools like get_competitor_price or get_brand_snapshot.

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 implies usage context: when you need promotion details for a domain. It does not explicitly mention alternatives or exclusions, but the focused purpose makes the right scenario obvious. No contradictory guidance is present.

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