Recomputes event-contract trading fees per fill and per order from an effective-dated venue fee profile, and diffs the recompute against a reported fee. Venue-neutral: the fee family and its parameters are data, with shipped effective-dated profiles for Kalshi (per-fill trade fee ceiled to $0.000001 plus the pinned per-order rounding accumulator, reproduced from both pinned worked examples), Polymarket global (pinned category rate table with 5-decimal rounding and the 0.00001 USDC minimum), Polymarket US (CFTC 40.6(d) taker coefficient history), and a caller-declared generic profile. Every fee path is integer BigInt arithmetic; conservation (order fee = fill trade fees + net carried rounding) is checked on every order. This tool recomputes declared terms and reports arithmetic only: no endorsement by any venue, no trading advice, no account or order identifiers by schema, values that look like identifiers are refused and never echoed.
| Family | Rule | Outcome |
|---|---|---|
| parabolic / multiplier | theta x C x p x (1-p), times the effective series multiplier; prices are integer micro-dollars and every product is BigInt | per-fill fee |
| linear / flat / rebate_share | theta x C per contract; a fixed micro amount per contract; a maker rebate equal to a declared share of the taker-equivalent fee (never a negative theta) | per-fill fee |
| Kalshi accumulator | per-fill trade fee ceiled to $0.000001; rounding overpayment carries across the order's fills and is rebated in $0.01 (non-direct) or $0.0001 (direct) increments, capped so a fill's net fee never goes negative - the pinned worked examples are golden vectors | order fee + carry |
| Polymarket global | pinned category table (crypto 0.07 ... combos 0.05), 5-decimal rounding, fees under 0.00001 USDC round to zero | per-fill fee |
| Polymarket US | taker theta 0.06 from 2026-07-07 and 0.0695 from 2026-09-17 (CFTC 40.6(d) letters); combo curve C x p x [0.0695(1-p) + 0.04(1-p)^4] from 2026-09-25 | per-fill fee |
| fee_check | per order, the recompute is diffed against the caller-reported fee: MATCH, OVERCHARGE (reported above the recompute) or UNDERCHARGE | verdict |
| conservation | every order checks order fee = fill trade fees + net carried rounding; the flag is set on every completed run | check |
| refusals | unknown profile, malformed as_of, identifier-like order or outcome labels (never echoed), malformed fields, out-of-domain inputs | refusal |
Adjacency: art-211 and art-212 compute whole-order fees inside their analyses; this node is the standalone per-fill recompute and edits neither. Rates and rounding rules come from pinned venue documentation only; any rule without a pinned source ships caller-declared. Profiles for Robinhood, Crypto.com, ForecastEx and Coinbase are deferred.
Copy this paragraph into Claude, OpenClaw, or any MCP-aware agent to run this exact tool, with this sample, and verify the artifact.
Run the AINumbers MCP tool `recompute_event_contract_fee`. Task: Recompute event-contract trading fees per fill and per order from an effective-dated venue fee profile (Kalshi with the pinned rounding accumulator, Polymarket global category rates, Polymarket US CFTC 40.6(d) history, or caller-declared generic) and diffs against a reported fee: MATCH, OVERCHARGE or UNDERCHARGE.
Call it with arguments: {"policy_parameters":{"profile":"kalshi","as_of":"2026-10-31","orders":[{"order_label":"fcm-example-one","role":"taker","fills":[{"contracts":1,"price_micro":55000}],"reported_fee_minor":5000}]}}
Verify before trusting: call `verify_execution_hash` on mcp.ainumbers.co (https://mcp.ainumbers.co/mcp) with the parameter `claimed_hash` set to the returned `execution_hash`, passing the full artifact the run returned (the object containing `policy_parameters` + `output_payload` + `execution_hash`; equivalently `policy_parameters` + `output_payload` with `claimed_hash`), not the bare hash string.
Return the ledger link https://ledger.ainumbers.co/ so a human can re-verify without contacting us.
PII rule: All inputs are processed locally in your browser. No data is transmitted. Do not enter real personal data — use synthetic or anonymised inputs only.
Over MCP, the run happens on the AINumbers worker. No AINumbers server stores your inputs.
Open the tool with the sample prefilled: https://ainumbers.co/chaingraph/794-event-fee-recompute.html#p=v1.H4sIAAAAAAAA_wGtAFL_eyJwcm9maWxlIjoia2Fsc2hpIiwiYXNfb2YiOiIyMDI2LTEwLTMxIiwib3JkZXJzIjpbeyJvcmRlcl9sYWJlbCI6ImZjbS1leGFtcGxlLW9uZSIsInJvbGUiOiJ0YWtlciIsImZpbGxzIjpbeyJjb250cmFjdHMiOjEsInByaWNlX21pY3JvIjo1NTAwMH1dLCJyZXBvcnRlZF9mZWVfbWlub3IiOjUwMDB9XX3OGnsFrQAAAA