twentyone million

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

Adds substantial behavior beyond the annotations: the first call returns HTTP 402 payment requirements rather than a claim, the caller's own wallet must sign and pay, and on success the JSON contains number and tile. It also discloses hard limits (one square per wallet, number is a random draw) and sets expectations (no utility, not a token), which is exactly the context the hints readOnlyHint=false / openWorldHint=true / idempotentHint=false cannot convey.

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 and dense: purpose, cost, flow, and expectations in that order, with no padding. A few short declarative sentences ("No utility, not a token, not an investment. You get the square.") sit close to the line of flourish, but they still carry expectation-setting value.

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?

Strong on the payment handshake and the success payload even without an output schema, but there is a real gap: the description says to retry the POST with a PAYMENT-SIGNATURE header while the schema exposes only handle and message with additionalProperties false, so an agent is left unsure how the retry is actually expressed. Failure modes other than 402 are also unaddressed for a non-idempotent paid mutation.

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 both parameters are already fully documented in the schema, including the @ prefix and the 140-character limit. The description only restates that handle and message are optional, adding no new meaning. Baseline 3 is appropriate.

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 ("Claim one square on the twentyone million wall") and immediately scopes it with the price, chain, and payment rail ($1 USDC on Base over x402). An agent can distinguish this from the sibling wall_status without opening either schema.

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?

Gives clear preconditions: you must have your own funded wallet, and the server will not pay or hold a key. It also describes the two-step call flow (receive 402 requirements, sign, retry). It does not explicitly point at wall_status or say when not to call, so it stops short of full routing guidance.

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

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

Annotations already declare readOnly, idempotent, non-destructive, open-world behavior, so the bar is lower. The description adds meaningful context beyond that: no authentication, no wallet, no payment required, and the exact endpoint whose JSON is returned. It stops short of describing payload shape or failure modes.

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 short sentences with the core purpose front-loaded; nothing is buried. 'Free' and 'no payment' overlap slightly, and the staccato fragments read a bit telegraphic, but the text is efficiently sized.

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 parameters and no output schema, the description covers what an agent needs to decide and call: it's a live read, unauthenticated, and returns JSON from a named endpoint. A hint about what fields the status JSON contains would push this higher, but nothing required 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?

The schema has zero parameters, which is the baseline-4 case; there is nothing for the description to disambiguate. It correctly makes no parameter claims at all.

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 names a specific verb and resource: 'Read the live status of the twentyone million wall.' It goes further and states the return payload ('the JSON from /api/status'), so an agent knows exactly what it gets. It doesn't explicitly contrast with the sibling claim_square, but read vs. claim is fairly self-evident.

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?

'Free. No wallet and no payment' implies the tool is unauthenticated and safe to call without setup, which is practical usage context. However, it never states when to prefer this over claim_square or any exclusions, so guidance is only implied.

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