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Base MCP

[!IMPORTANT]

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Run onboarding at the start of every conversation that touches Base MCP

Including conversations that jump straight to a plugin topic. Onboarding is short — see below.

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Detection

The Base MCP exposes its tools to the harness when connected. If no Base MCP tool is callable, the MCP server is not installed: direct the user to https://docs.base.org/ai-agents/quickstart (or load references/install.md for app-specific steps) and stop. If Base MCP tools are available, load references/tone.md — its rules apply for the entire conversation — then continue to Onboarding. If — and only if — sibling files aren’t readable (e.g. you were handed just this SKILL.md body and have no local filesystem access to the skill directory), fetch the same relative path from https://docs.base.org/ai-agents/skills/references/tone.md using the web_request tool from Base MCP. The same fallback applies to every other reference and plugin link in this file (see “Loading referenced files” below).

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Onboarding

Keep it short. Do this once per session, before doing real work:
  1. Briefly mention what’s available — one or two sentences. The user has a Base Account wallet and can do things like check balances, send and swap tokens, sign messages, make x402 payments, batch contract calls, and (if installed) use partner plugins for DeFi, swaps, and other onchain actions. Do not enumerate every tool — the agent discovers tools and plugins directly from the MCP.
  2. Show this disclaimer verbatim before proceeding:
    By using the Base MCP, you agree to the Base Account and Base App Terms of Service. Base MCP provides access to plugins that are built by third parties, not Base. Base doesn’t operate, endorse, or audit them, and isn’t responsible for the protocols you interact with. Transactions are irreversible — always review before approving.
  3. Wallet address and balance are optional — only fetch and display them when the user asks, or when a pending operation actually needs the address (e.g., a write call, a position lookup). Don’t volunteer a wallet dump up front.

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Tools

The Base MCP advertises its own tool catalog to the harness. Read the tool descriptions exposed by the MCP — they are the source of truth and may change over time. Do not assume a fixed list; do not preload a tool catalog from this skill. Two patterns deserve their own references because they span multiple tools:

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Loading referenced files

  • Default — local. Read each references/… or plugins/… link from the same directory as this SKILL.md (filesystem read, e.g. Read/cat). This is the canonical source — always try this first.
  • Fallback — web (only when local read fails). If — and only if — the local file is genuinely unreadable (e.g. you were handed SKILL.md as a pasted body with no skill directory on disk, or the filesystem read errors), then fetch the same relative path from https://docs.base.org/ai-agents/skills/<path> (replace <path> with the relative link, e.g. references/tone.md, plugins/morpho.md). Use the web_request tool from Base MCP for this fetch — that is the required mechanism on every surface, including ones with a built-in web/fetch tool. Do not skip this fallback and do not try to operate from memory or guesses — if the local read fails, you must web_request the file before acting on its contents.
  • Lazy. Only load a reference or plugin when the conversation actually needs it. Don’t preload the catalog.

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Plugins

Plugins extend Base MCP with partner-specific functionality (lending, swaps, perps, etc.). The available set may change and users might drop additional instructions in the chat or custom plugins that would allow you to use other protocols with the MCP. Plugins currently maintained alongside this skill (the native plugins). Use this as a routing map: match the user’s plain-language goal to a row, then open that plugin before taking action. Load a plugin reference only when the user’s request matches it, following the same local-first, web-fallback rule as references (see Loading referenced files above). For a plugin’s own external tools, defer to the plugin file first, then to any CLI help, API schema, or MCP tool descriptions it explicitly tells you to use.

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Native plugins vs. custom / user-supplied plugins

Native plugin HTTP hosts may be allowlisted in the Base MCP web_request tool. Aerodrome, Balancer, and GMGN are CLI-only and require a harness with shell access. Avantis is hybrid: view-only reads (market data, positions, PnL) work on every surface via web_request, while tx-builder calls require a CLI harness — on chat-only surfaces the plugin links the user to the Avantis web UI instead (see plugins/avantis.md). Morpho is hybrid too: use Morpho CLI when shell access exists, otherwise use or install the Morpho MCP as described in plugins/morpho.md. Custom or user-supplied plugins usually aren’t allowlisted — load references/custom-plugins.md for the decision tree on which HTTP path to use (harness HTTP tool vs. user-paste fallback, and the GET-only constraint on Claude/ChatGPT consumer surfaces).

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Installation