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

Annotations already declare readOnlyHint=true, but the description adds substantial behavioral context beyond that: the hard allowlist constraint, testMode affecting which stores appear, the special return fields for merchant invite links, and retry rules using sessionId. This is rich, actionable behavioral detail.

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 front-loaded with the primary purpose, followed by trigger conditions, testMode behavior, and auth retry rules. It is longer than minimal but every sentence carries operational instructions; a few repetitive 'Never' directives could be consolidated but overall it is efficiently structured.

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?

Despite having no output schema, the description explains what the tool returns (preferredStores + preferredStoreRoutingRu for merchant invite links), how testMode changes results, and how to handle sessionId. Combined with the annotations, this is sufficient for an agent to invoke the tool correctly in all described scenarios.

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 coverage is 100%, so the parameters are already documented. The description adds meaningful context by explaining when to pass sessionId ('If AGENTPAY_API_KEY required and you already have sessionId from this chat: pass sessionId and retry') and by noting that need is optional and that peek_stores may be preferable for a quiet offer.

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 as 'List stores on this agent's allowlist', using a specific verb and resource. It differentiates itself from siblings by explicitly stating it is not a search tool and directing to peek_stores for 'найди'/'сравни'/'подбери'.

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?

Provides explicit trigger phrases ('магазин', 'где можно потратить') and explicitly says when NOT to use it, instead calling peek_stores first. It also includes precise instructions about sessionId handling and testMode behavior, leaving no ambiguity about invocation context.

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