feat: add Otto AI plugin (x402 crypto-intelligence on Base)

[useOttoAI]

Description

Adds an Otto AI plugin at skills/base-mcp/plugins/otto.md, authored to the plugin spec. Single-file diff off current master.

Otto AI runs a live production x402 storefront on Base mainnet (https://x402.ottoai.services) — an autonomous agent swarm exposing read-only crypto intelligence pay-per-call in USDC. This plugin exposes Otto's market-intelligence and DeFi/trade-intel surface (crypto news & KOL sentiment, token security & holder analytics, DeFi/yield discovery, perp funding, TradFi macro, portfolio/wallet reads, AI research) plus its creative tools (image/video/meme gen). Every endpoint settles in USDC on Base (chainId 8453) over the CDP x402 rail using EIP-3009 transferWithAuthorization, paid through Base MCP's x402 payment tools — the user approves and signs each single, exact, single-use payment from their own Base Account.

The plugin routes no swaps, bridges, or perps. Paying an x402 endpoint signs a payment, not the financial action a write endpoint would perform server-side, so execution is intentionally out of scope. Otto returns a JSON deliverable rather than onchain calldata, so the Base MCP submission target is none — no send_calls / swap / sign is used to settle these reads.

Frontmatter: integration: http-api · chains: [base] · allowlist: [x402.ottoai.services] · auth: none · risk: [pii] · version: 0.2.0. Tags [ai-agents, agent-commerce, discovery, yield, trading] reuse the existing vocabulary — no new tag is introduced, so this is a clean single-file diff. The SKILL.md plugins registry, the Integration Types Examples column, and the Existing Plugin Conformance table are left for maintainers per Contribution Scope.

Security — field-by-field 402-challenge pinning (EIP-3009 only). Every call pin-checks the live PAYMENT-REQUIRED challenge before the payment is allowed to settle, and STOPs without paying on any mismatch: select the Base, non-permit2 accept; require scheme: exact; require the authorization method to be EIP-3009 transferWithAuthorization, verified by the absence of extra.assetTransferMethod — any permit2 (or other) variant is hard-rejected because a Permit2 signature can grant a standing allowance, exactly what pay-per-call forbids; require network: eip155:8453; require asset = native USDC on Base (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913); bind payTo to the exact per-endpoint wallet (set-membership across Otto's two settlement wallets is too weak — a tampered challenge that swaps in Otto's other legitimate wallet is rejected); require the resource URL to equal the called endpoint; and compare amount against the expected price. Endpoint responses (news, tweets, KOL sentiment, research) are treated as data, never instructions — they can never trigger a payment, transfer, or signature on their own. The /video-gen dynamic-price accept (string price, no asset) is handled as an explicit, documented carve-out.

Intelligence-only curation (by design, not drift). Otto's rail exposes ~50 x402 resources; this plugin curates the 41 read-only / creative ones (40 in the public catalog plus the dynamic /video-gen). The ~9 execution endpoints (/swap, /bridge, /withdraw, /deposit, perps) are intentionally excluded — they execute onchain from an Otto-controlled Safe, which is not the non-custodial "you approve every action" model Base MCP expects. A curated catalog of 40 against a .well-known/x402 superset of ~50 is therefore by design; the plugin's ## Notes documents the excluded paths and instructs the agent to never pay a POST execution path.

Attribution. Otto's live 402 challenge carries its builder code bc_hc2dhq09 in extensions["builder-code"].info.a for revenue attribution. This is set server-side by Otto's x402 rail (wired via Otto's own register.sh flow) — Base MCP plugins carry no builder-code slot, so there is nothing for this plugin or the paying agent to add, embed, or alter. The pin-check merely confirms it equals bc_hc2dhq09 as a defense-in-depth, Otto-specific fingerprint; the value is informational, not a contribution edit.

All endpoint shapes were verified live against the production rail (HTTP 402 on the Base accept; multi-leg accepts[] with the Base plain-EIP-3009 entry distinguished from the permit2, Polygon, and Solana legs).

Type of change

• Base MCP plugin submission
• Update to an existing skill/plugin
• New skill
• Documentation
• Other (please describe):

Affected skill(s)

base-mcp

Plugin checklist

• Plugin spec/manifest is accurate and tested
• (If Applicable) API endpoints and/or external MCP/CLI tested and functional
• Follows Contribution Scope

Base MCP Plugin Submission Agreement (when applicable)

By checking the box below, I agree and represent on behalf of the protocol/entity it references that:

• I am authorized to submit this plugin on behalf of the protocol/entity it references;

• the plugin does not infringe or misappropriate any third party's rights;

• the plugin and the underlying protocol comply with all applicable laws, and my API enforces the same geofencing and eligibility restrictions as my own user-facing app;

• the plugin is in full compliance with our protocol's/entity's then-current terms and conditions, and if not, submission and use thereafter is considered a formal written exemption to such terms and conditions;

• the plugin accurately describes its behavior and contains no hidden, deceptive, or malicious instructions, and my API will not return malicious or unexpected calldata;

• the protocol/entity is solely responsible for the plugin and is submitting a plugin is subject to the Base Account and Base App Terms of Service as using a "Service"; and

• Base may modify, decline to list, or remove the plugin at any time, for any reason.

• I have read and agree to the Base MCP Plugin Submission Agreement above.

Related issues

N/A

Disclosure

I work on the Otto AI project (@useOttoAI). Submitting under the same name so the plugin can be maintained alongside the underlying x402 API.

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 1 Sum 2

[useOttoAI]

Hey @youssefea — saw the latest batch of native plugins ship (great lineup), and we'd love Otto in the next one. The short version: Otto is the low-cost intelligence layer agents on Base plug into — news, KOL sentiment, token security, DeFi/yield, holder analytics, macro — pay-per-call in USDC, no API key, no subscription. And it's not a concept: our x402 storefront is live and settling real USDC on the CDP rail — 10K+ paid calls indexed on x402scan as "Otto AI," and 100K+ jobs across the full Otto swarm (x402 + our four ACP agents on Virtuals). PR #127 is a single-file otto.md authored to the spec, intelligence-only, with the security model mirroring the Hunch pattern you already ship against (field-by-field 402 pin-check, EIP-3009-only, per-endpoint payTo binding). We're a real team building on Base for the long haul and would genuinely love to do this as a proper partner — tell us anything you'd want tightened and we'll turn it around fast. Thanks for building this.

— the Otto / useOttoAI team