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

With no annotations, the description carries full burden. It discloses that checking is free, activation triggers a payment challenge, and returns a token for 30-day unlimited calls. It also mentions per-call costs and trial period. However, it omits behavior for already-subscribed users and does not fully describe the status check response.

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 long and mixes instructions with pricing details. It front-loads the two main actions but then becomes dense with payment flow, signing, and token usage. A more structured format (e.g., bullet points) would improve clarity without losing information.

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?

No output schema is provided, so the description must cover return values. It mentions returning an X-SUB-KEY token for activation but does not describe the response for status checks. Error scenarios (e.g., invalid agentId, already subscribed) are not covered. Adequate but incomplete.

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% with basic descriptions. The tool description adds meaningful context: 'agentId' links the subscription, 'activate' requests the payment challenge. This enriches beyond the schema, though the schema already covers the parameter names and types.

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 states two distinct actions: checking subscription status (free) and activating the monthly plan via the 'activate' parameter. It explicitly mentions linking an agentId and contrasts with per-call pricing, making the tool's purpose 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?

The description provides explicit when-to-use guidance: check status without 'activate', or activate the plan with 'activate:true'. It also mentions the alternative of per-call pricing until subscribed and details the activation flow (402 challenge, signing, retry). This fully guides the agent on selecting the correct mode.

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