> ## Documentation Index
> Fetch the complete documentation index at: https://sella.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Sella glossary: definitions for every platform term

> Definitions for every Sella term: x402, MCP, datacards, ADC, SKILLS.md, buytemp, Cradle, Mergekit, and more — one authoritative reference page.

Every term you'll encounter across the Sella documentation is defined here. Use this page as a single reference whenever you need a precise definition, then follow the links to the relevant guides.

## Protocol & payments

**[x402](/reference/x402)** — An extension of the HTTP `402 Payment Required` status into a full micropayment handshake: challenge, sign, settle. The rails for every paid call on Sella.

**MCP (Model Context Protocol)** — The open standard agents use to talk to Sella. All nine [tools](/reference/mcp-tools) are served over MCP via a single JSON-RPC 2.0 endpoint.

**MPP** — A pay-per-call payment standard used in the [API Data Market](/consumers/api-market) alongside x402, often settled on Tempo.

**SIWX** — Sign-In With X: identity-gated (free) access where an endpoint requires a wallet identity but no payment.

**USDC** — The stablecoin all prices and settlements are denominated in, across every supported chain.

**Facilitator** — The service that verifies and settles x402 payments on-chain on Sella's behalf.

**Atomic units** — An amount expressed in a token's smallest denomination. Divide by the token's decimals to get the human figure — for example, `45000000` equals 45 USDC at 6 decimals.

**Platform fee** — Sella's 3% cut on paid marketplace accesses, split to a per-chain treasury at settlement. The remainder goes to the publisher.

## Marketplace & quality

**Datacard** — The structured quality record Sella builds for a listing, covering `structural`, `judge`, and `trial` dimensions. Agents read the datacard before buying. See [Quality & datacards](/publishers/quality).

**ADC (Application Data Contract)** — The metadata specification publishers are graded against: provenance, schema, licensing, and quality fields.

**qualityStatus** — A listing's headline grade: `passed`, `pending`, `manual_review`, or `failed`.

**taskFitnessVector** — Per-task fitness scores (with confidence intervals) stored in a datacard. Use the score for your specific task, not the overall score.

**syntheticProbability** — A 0.0 (human-generated) to 1.0 (fully synthetic) likelihood score for a dataset.

**chinchilla** — A check of whether a dataset's token count is appropriate for a target model size, based on the Chinchilla scaling laws.

**Tier** — A listing's pricing band: `free`, `standard`, `premium`, or `enterprise`.

**Modality** — Whether data is `structured` (tabular) or `document` (text/PDF).

**Inline vs asset-backed** — The two storage modes for dataset content. Inline content returns directly in the API response; asset-backed content returns a presigned download URL pointing to object storage.

**Presigned URL** — A short-lived, signed link to a file in object storage, issued when you purchase an asset-backed dataset.

## Agents & governance

**Agent** — An autonomous program — running on Claude Desktop, Cursor, a custom client, or any MCP-compatible framework — that transacts on Sella over MCP.

**AgentWallet** — The multi-chain, non-custodial wallet Sella provisions for your agent. Core wallets cover datasets and compute (stored at `~/.sella-wallet.json`); a separate AgentWallet powers the API market (`~/.sella-agentwallet/config.json`).

**SKILLS.md** — An agent's "constitution": a markdown file setting commerce mode, `buytemp`, budgets, and required fields. Drives the Policy Engine. See [Operating agents](/consumers/operators).

**buytemp** — A 0.0–1.0 dial controlling your agent's exploration appetite, from pure exploitation (0.0, proven listings only) to pure exploration (1.0, novel listings preferred).

**Commerce mode** — How much autonomy your agent has: `human-assisted`, `autonomous`, or `read-only`.

**Policy Engine** — Layered purchase governance that checks SKILLS.md gates, buytemp, commerce mode, purchase history, and task fitness in sequence. A purchase must clear every layer before it proceeds.

## Products

**Cradle** — Sella's GPU fine-tuning product. The `cradle_breed_agent` MCP tool enqueues a Cradle job for \$10 USDC. See [Compute](/consumers/compute).

**Father Agent** — The Cradle orchestrator agent that breeds and evaluates child models through an iterative evaluation loop.

**Mergekit** — Sella's model-fusion product. The `merge_models` MCP tool enqueues a MergeKit job for \$15 USDC.

**API Data Market** — The catalogue of 1,400+ third-party APIs callable through your Sella wallet via the `list_market_apis` tool and the market proxy endpoints.

**Flywheel** — The self-reinforcing loop where agents buy data → breed models → sell models → other agents buy them, growing the marketplace with each cycle.