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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds genuinely new behavioral facts: it is deterministic, free with no payment or account required, it never guesses (unstateable steps are marked documented:false or not_documented), and it does not pay or sign on the caller's behalf.

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 with purpose, but it is one dense block that repeats the payer object/example already present in the schema and packs cost formatting, verifier paths, and caveats into a single run-on sentence. Nothing is wasted exactly, but the structure is hard to scan.

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 usefully details what comes back: per payment type an ordered list of machine-readable steps, the cost fields, USD conversion only for recognised USD stablecoins, and the documented:false convention. Minor gaps remain around tracing/labeling behavior details, but coverage is good for a 5-param, 0-required read-only tool.

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 description still adds meaning: it clarifies target='verifier' selects the Verifier's own live price/free paths, that payer must be an object (not a string) and omitting it shows every option, and that agent_id is an unauthenticated stats-only label and trace_id continues a prior Concierge conversation.

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?

Names a specific verb and resource — explains step-by-step how a listing is paid for and what it costs — and enumerates the exact output shape (ordered steps, cost in amount/asset/network/USD, cheapest usable option). It is clearly distinguishable from siblings like describe_listing and get_listing, which describe content rather than payment paths.

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?

States the two input modes ('Give listing_id, or target verifier') and sets a scope exclusion ('This tool only explains; it never pays or signs for you'), plus that it is free and requires no account. It does not explicitly name a sibling alternative to use for other needs, so it falls short of a full when/when-not/alternatives statement.

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