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

With no annotations, the description must disclose behavior itself, and it does: the session is short-lived, the user signs in their own wallet via injected/mobile/WalletConnect, and the agent polls/retries. It also adds a key security constraint that no private keys or seed phrases are accepted. It omits expiration/side-effect details but covers the most critical behavioral expectations.

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 two sentences and immediately states the core action and flow. Every phrase adds meaningful context, and the final security note is high-value, making it efficient and well-structured.

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 large parameter surface, nested objects, and no output schema, the description provides only a high-level flow and leaves the agent guessing about required arguments, return shape, and error behavior. It does not mention that a sessionId would be returned or how to map params. This is insufficient for a tool of this complexity.

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 schema has 43 parameters with only 33% described, and the description does not map any of these to the signing flow or explain which ones are relevant. It mentions the signing URL and retry concepts but offers no parameter-level semantics beyond the schema. With such low coverage, the description should compensate but does not.

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 verb and resource: 'Create a short-lived hosted wallet signing session,' and clearly frames the intended clients and sign-in flow. This distinguishes it from polling/status siblings like x402_payment_session_status and from connect_wallet by focusing on creating a session rather than connecting.

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 clearly describes the intended context—ChatGPT/MCP clients needing a user wallet signature—and the post-sign flow of polling and retrying with X-PAYMENT. However, it does not explicitly name alternatives or state when not to use this tool, so it stops short of full guidance.

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