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

Annotations only carry readOnlyHint=false and destructiveHint=false, which is minimal negative information, so the description carries the behavioral burden. It discloses that the tool returns a challenge message (implying no state change at this step), that new wallets are 'auto-registered on first verify' (deferring side effects to the next step), and that a paid plan unlocks usage — pricing context an agent would not otherwise know. The two-chain supported behavior is also disclosed beyond the schema.

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?

Three sentences, each earning its place: the first states the core action and return value, the second adds chain support and the successor tool, the third covers registration and billing implications. Core purpose is front-loaded. The pricing sentence is arguably secondary but is valuable behavioral context. No redundancy or filler.

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 simple 3-parameter tool with 100% schema coverage, no output schema, and thin annotations, the description covers what the tool does, what it returns (challenge message), the two supported chains, the required follow-up step, and the billing consequence. Minor gaps remain — challenge validity duration and return format details — but nothing an agent needs to invoke it correctly 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%, so the baseline is 3; the schema already documents chain auto-detection, wallet_type defaults by address shape, and address formats. The description adds marginal reinforcement ('base58 Ed25519' vs '0x') that maps to wallet_address validation, but it does not add new parameter semantics the schema lacks. This is a fair baseline, not a bonus.

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+resource: it is 'Step 1 of registering (or logging in) a user with a wallet keypair' and returns 'a challenge message to sign with the wallet's private key.' It clearly distinguishes itself from the sibling auth_wallet_verify by positioning itself as the first step and explicitly naming the follow-up. Chain scope (Solana base58/Ed25519, EVM 0x) further tightens the purpose.

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 clear workflow context: 'Step 1' and 'Follow with auth_wallet_verify' tell an agent exactly when this tool fits in a multi-step flow relative to a named sibling. The 'no browser needed' line also differentiates it from browser-based auth flows. It does not explicitly state when NOT to use alternatives like auth_connect or auth_resolve, but the workflow framing is enough to route correctly.

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