naulon

Quote the toll (free price probe)

naulon_quote

Read-only

Probe the real x402 toll for a source WITHOUT paying — the free 402 price check. Returns the author price, the buyer's true total (when the publisher adds extra settlement legs such as an operator fee, the total is higher than the author price), and the settlement terms. gated:false means one thing only — the origin answered 2xx, so it is a genuinely free read you may just fetch. Anything else returns refused:true with the reason in note: a refusal to reach the url (off-gate identity, or operator policy such as a kill-switch or deny-list), a 404, an unreachable origin, or a malformed 402. A refused url is NEITHER payable nor free — do not fetch it and do not report it as free; retry or fix the url.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "slug": "<slug>"
    },
    "name": "naulon_quote"
  }
}

Input Schema

Name	Required	Description	Default
`url`	No	Canonical URL from naulon_discover (the source's real link). When present it is probed VERBATIM; absent, the slug is reconstructed to the /essays/<slug> template.
`slug`	Yes	Source slug from naulon_discover.

Output Schema

Name	Required	Description
`legs`	No	Present only for a multi-leg toll (e.g. author + operator fee).
`note`	No
`asset`	No
`gated`	No	True if the source requires payment; false if it is a free read. Absent on a refusal (see refused).
`payTo`	No	The author payee address.
`network`	No
`refused`	No	True when this url is NEITHER payable NOR free, so there is nothing to act on: the server refused to reach it (off-gate identity, or operator policy such as a kill-switch / deny-list), the path was not found (404), the origin was unreachable, or the gate answered a malformed 402. The reason is in note; do NOT fetch it, and do NOT treat it as free. Mutually exclusive with a gated/free result.
`priceUsdc`	No	The author leg price in USDC.
`totalUsdc`	No	The buyer's true total across all settlement legs.
`settlement`	Yes	The chain + token the toll settles on. Check settlement.testnet before calling a price real money.
`amountAtomic`	No	The author amount in atomic units (micro-USDC string).
`refusedReason`	No	WHY it was refused, always present when refused is true. `policy` — we would not even probe it (off-gate identity, kill-switch, deny-list): the url is out of bounds, so do not retry it. `not_found` — the path is wrong; re-quote with the canonical url from naulon_discover. `unreachable` — the origin or gate is down; the url may be fine, so retry later. `malformed` — the gate answered a 402 we cannot read; it is misconfigured, and retrying will not help. Two of these are the caller's to fix and two are not, which is why this is a field and not prose.

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 11, 2026

TDQS

A4.1/5.0

Behavior4/5

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

Annotations already cover the safety profile (readOnlyHint, destructiveHint false, openWorldHint true), and the description adds real semantic disclosure beyond that: the precise meaning of gated:false, the meaning of refused:true, and an enumeration of causes (off-gate identity, kill-switch, deny-list, 404, unreachable origin, malformed 402). It does not discuss cost, rate limits, or latency of the probe itself.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The core distinction (free probe, no payment) is front-loaded in the first clause, and the refusal-handling rule is stated as a self-contained final sentence. The parenthetical about operator fees is longer than needed but carries genuine information about why totals differ.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return fields need not be re-explained, and the description focuses on the one thing the schema cannot convey: how to interpret gated vs refused and what an agent must not do with a refused url. Coverage of the refusal/reporting edge cases is thorough for a two-parameter probe.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%: the schema already explains that url is probed verbatim and that slug is reconstructed to the /essays/<slug> template when url is absent. The description adds nothing about either parameter, so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource ('Probe the real x402 toll for a source') and immediately names the defining scope constraint ('WITHOUT paying — the free 402 price check'). It also enumerates what comes back (author price, buyer's true total, settlement terms), so an agent knows this is a read-only price inspection rather than a fetch or a retrieval.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

It gives clear when-to-use context (probe the toll before committing) and explicit when-NOT behavior: a refused url is 'NEITHER payable nor free — do not fetch it and do not report it as free; retry or fix the url.' It does not name a sibling tool as the alternative path, so routing against naulon_retrieve must be inferred.

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

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