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

Annotations already mark readOnlyHint=true, so no contradiction exists. The description goes beyond annotations by revealing that the address is the owner's saved data, how to handle missing fields by asking and then calling save_delivery_address, and the sessionId retry rule when AGENTPAY_API_KEY is required. These are meaningful behavioral details not present in the annotations.

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 core function and then uses compact imperative sentences for usage rules. Every sentence carries distinct guidance: when to call, what to do on missing fields, what to never do, and how to handle auth. No filler or redundancy.

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's simplicity and full schema coverage, the description provides almost everything an agent needs: the returned field set, call context, missing-data handling, and auth caveats. A minor gap is that it does not explicitly describe the response container or error/empty-address shape, but the field enumeration and 'if fields are missing' instruction largely cover this.

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 only parameter, sessionId, is already fully documented in the input schema with 100% coverage, including the exact condition for passing it. The description does not add new parameter-level meaning beyond what the schema already provides, so a baseline score 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 and resource: 'Get the owner's saved AgentPay home address split into courier fields', followed by an enumerated field list. It clearly differentiates itself from the sibling save_delivery_address by stating when to call it and what to do after. The purpose is unambiguous.

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?

Explicit usage conditions are provided: 'Call before create_purchase or when the user asks «какой адрес», «куда везти», «домофон».' It also gives explicit when-not guidance: never invent fields, never begin_agent_link again, never ask the owner to edit connector settings or reconnect. This fully routes the agent between this and related tools.

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