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

Annotations declare readOnlyHint: false, which the description honors by describing a state-changing flow starter. The description adds value beyond the annotations by disclosing that no API key is required and by giving hard constraints: 'Never invent keys', 'Never ask the owner to paste ap_ from the cabinet'. It does not contradict any annotation. Minor gap: it doesn't state what the response payload contains beyond openUrl.

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 but every sentence earns its place: purpose, exclusions, parameter guidance, and critical prohibitions are all relevant. It is front-loaded with the purpose before the constraints. Slightly verbose with the repeated 'Never' constraints, but each carries distinct behavioral weight.

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 flow-starter with a single fully-documented parameter and no output schema, the description covers the essential behavioral contract: the preconditions, the follow-up step (poll_agent_link), the openUrl action, and the prohibitions. It relies on the schema for the client enum. It could more explicitly describe the return shape, but the openUrl reference covers the key output an agent needs to act on.

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% and the schema already documents the client parameter thoroughly, including allowed values and the warning against inventing a different brand. The description restates the client enum but adds no new meaning beyond the schema, so the baseline 3 applies.

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 names a specific verb (start) and resource (AgentPay browser connect), and explicitly scopes it: 'only when a personal tool needs the owner's data' while clarifying that MCP setup itself needs no authorization. This clearly differentiates it from sibling auth tools like start_dixy_call_auth and from setup flows.

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 gives explicit when-to-use guidance ('only when a personal tool needs the owner's data'), a clear when-not-to ('Never start an authorization flow during setup'), and the full invocation sequence (open openUrl so the owner clicks Разрешить, then poll_agent_link). It names the follow-up sibling tool and the required client value format.

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