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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=true, and openWorldHint=true. The description adds meaningful behavioral context beyond annotations: it discloses that the tool requires caller approval, that it never auto-chains/signs/submits, and that the private key stays client-side. It does not contradict annotations. It could add more about what the response contains or what side effects occur, but the description's explicit non-behaviors are valuable.

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 three sentences, each earning its place: the first states the tool's core purpose, the second explains the critical Solana-CCTP requirement, and the third states exclusions. It is front-loaded with the primary purpose. Slightly dense but not bloated.

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 10-parameter tool with no output schema, the description covers the most critical behavioral context: caller approval, ephemeral keypair handling, and non-chaining behavior. It does not describe the return value or what happens after creation, but the sibling tools (assetfare_v2_session_get, assetfare_v2_session_observe_output) suggest the follow-up flow is handled elsewhere. The description is complete enough for an agent to call it correctly without opening the schema.

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 description coverage is only 10%, so the description must compensate. It does: it explains the event_signer_public parameter's purpose and security model, and it clarifies the session_token requirement. However, it does not explain the wallets map, idempotency_key, or amount_usd semantics beyond what the schema provides. The description adds meaning for the most complex parameter (event_signer_public) but leaves other parameters to the schema.

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 states a specific verb ('create'), a specific resource ('/v2/session'), and a distinctive qualifier ('Explicit caller-approved receipt-driven'). It also names the sibling it is not ('Never auto-chains, signs, or submits'), which distinguishes it from other session tools in the sibling list. The name alone is ambiguous, but the description resolves it.

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 explicitly states when this tool is appropriate: caller-approved, receipt-driven session creation. It names the Solana-CCTP route requirement (event_signer_public from a fresh ephemeral keypair) and the session capability token requirement. It also states what it does NOT do ('Never auto-chains, signs, or submits'), which implicitly routes the agent to sibling tools for those behaviors. This is strong usage guidance.

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