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

Goes well beyond the annotations by disclosing the fee model (1% standard, 0.8% for subscribers, read from the router for `from`), that a dry-run is performed against `from`, and that the result is unsigned steps the buyer signs themselves while OwlGate never signs or holds funds. This also explains why readOnlyHint=true is consistent despite the name 'buy'.

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, front-loaded with what the tool produces, and every clause carries information. The fee clause is dense parenthetical detail but is genuinely needed for cost expectations, so little is wasted.

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 output schema, the description carries the return contract ('Returns steps for the buyer to sign and send') and the safety model, which is adequate for a 3-parameter build-transaction tool. It leaves minor gaps around failure modes, such as what happens if the listing is gone or the price moved, and whether the quoted price is binding.

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, but the description adds real meaning: `cp` and `tid` must be sourced from a deals or fair_price item, and `from` doubles as the buyer wallet used for the fee-tier lookup and the dry-run. That linkage between parameters and the fee/dry-run behavior is not in 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?

States a specific verb and resource ('Unsigned transaction to buy one TapeOut rig') plus the venue (BNB Chain, OwlGate router), and immediately clarifies that it produces a signable transaction rather than executing a purchase. This distinguishes it from execution-style siblings like xl_fill and from discovery siblings like deals and fair_price.

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 concrete prerequisite guidance: 'Use cp + tid from a deals or fair_price item,' which tells the agent where the identifiers come from and which siblings feed this tool. It does not state when-not to use it (e.g., rig already sold, or when the caller wants to sign/send directly via another tool), so it falls short of full when/when-not coverage.

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