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

Annotations already mark the tool as read-only, and the description reinforces this with 'Never change limits, freeze, auto-topup, or allowlist.' It also discloses observable behavior: 'On every error read recovery: say userMessageRu, open openUrl in the browser,' plus authentication retry rules and the test-mode exception. This adds substantial context beyond 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 dense and front-loaded with purpose and triggers, and nearly every sentence carries operational value. However, it is a long run-on block of directives without paragraph breaks or list formatting, which slightly reduces scannability.

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 tool with one optional parameter and no output schema, the description is complete: it explains when to call, what the catalog contains, how to handle errors, authentication conditions, and explicit safety boundaries. No critical information an agent needs is missing.

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 input schema already documents sessionId thoroughly at 100% coverage. The description adds conditional value by saying 'If AGENTPAY_API_KEY required and you already have sessionId from this chat: pass sessionId and retry' and 'Never invent a sessionId,' which clarifies when and how to use the parameter in practice.

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 opens with a specific resource: 'Full catalog of AgentPay failures with RU copy, cabinet deep links, and recovery.openUrl.' It clearly identifies what the tool returns and gives concrete trigger phrases, making it distinguishable from sibling tools like get_faq or get_payment_status.

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?

It explicitly states when to call ('Call when something failed', 'before explaining a 4xx') and provides trigger keywords. It includes strong when-not guidance ('Never change limits... Never begin_agent_link again. Never web-search.'), though it does not name alternative sibling tools for fallback cases.

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