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

Goes well beyond the annotations (readOnlyHint=false, idempotentHint=false, openWorldHint=true) by disclosing what the call actually produces and its consequences: a full-scope key shown once, auto-adopted on this connection, credentials for the web cabinet, a zero starting balance, and a per-IP hourly rate limit. This is exactly the operational context annotations cannot carry.

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?

Front-loaded with the action and its payoff, then the gating condition, then the follow-up instructions. It is dense but nearly every clause carries new information; the api_key/cabinet_url/mcp_personal_url passage is slightly overloaded for a single sentence and could be split for scanability.

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?

With no output schema, the description still tells the agent what comes back (api_key, generated login/password, cabinet_url, mcp_personal_url) and what to do with it next time. Combined with the zero-balance and rate-limit caveats, nothing an agent needs before invoking this call 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?

Schema coverage is 100% and already documents each optional field, so the description's contribution is explaining what the generated login/password are for (opening the cabinet at cabinet_url) and that everything is optional. It does not add format or validation detail for 'agent', 'email' or 'telegram', hence not a 5.

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?

States a specific verb and resource ('Opens a new SnapEX Pay merchant account') and immediately names what it produces: a merchant API key with all scopes. It is unmistakable against the sibling set, where get_account reads and everything else (create_invoice, create_payout, ...) operates on an already-existing key.

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 when-to-use and when-not-to-use: 'Call it once, only when you have no key yet (other tools answer "unauthorized")'. That gives the agent both the triggering condition and the observable symptom that selects this tool over any sibling.

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