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

Annotations already cover safety (readOnly, idempotent, non-destructive, openWorld). The description adds behavior the annotations cannot express: each successful call costs $0.001 USDC via x402 on Solana, and the same operation is reachable over HTTPS POST. That payment/auth context is genuinely valuable and not repeated from structured fields.

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 result statement is front-loaded, followed by domain constraints, then pricing and endpoint. Every sentence carries distinct information — semantics, input validity, cost, transport — with no 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?

With only one parameter, no output schema, and rich annotations, the description covers what is needed to call it: the input domain, the rejection rule, the cost, and the transport. The remaining gap is sibling disambiguation within the large kaprekar family and the exact shape of the response.

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 0%, so the description must carry the load, and it does add meaning beyond the raw min/max: n is a four-digit value treated as 0–9999 and repdigits (0000, 1111, …) are rejected as invalid. It falls short of clarifying leading-zero handling or whether rejection is an error versus a defined result.

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 resource and result: the terminal value that the four-digit Kaprekar routine reaches (6174). An agent can tell it returns a constant rather than a chain or a step. However, it never distinguishes itself from the sibling cluster kaprekar, kaprekar_chain, kaprekar_step, kaprekar_steps, which is the main ambiguity.

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?

Usage is only implied: it states that n runs 0–9999 and that a repdigit is rejected, which lets an agent infer the valid input domain and that repdigit checks belong elsewhere. There is no explicit statement of when to pick this over kaprekar_chain or kaprekar_steps, and no mention of the sibling that handles rejection cases.

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