Codex MRL — Maximum Residue Limits (FAO/WHO Codex Alimentarius)

The internationally agreed legal ceilings for pesticide residues and veterinary drug residues in food, adopted by the Codex Alimentarius Commission. Codex MRLs are the reference point for food trade — a shipment rejected at a border is usually rejected against one of these numbers.

Part of Pipeworx — an MCP gateway connecting AI agents to 1573+ live data sources.

This is the permission side of food chemistry. The safety side — the Acceptable Daily Intakes and toxicological evaluations behind the limits — is the jecfa pack; veterinary drug records here carry a jecfa_chemical_id that links the two.

Tools

Tool	What it answers
codex_pesticide_search	Find a pesticide by name → id
codex_pesticide_mrls	One pesticide → ADI, residue definition, and its limit in every commodity
codex_commodity_search	Find a food commodity by name → id
codex_commodity_mrls	One food → every pesticide limit that applies to it
codex_vetdrug_search	List or search the 85 veterinary drugs
codex_vetdrug_mrls	One drug → limits by species and tissue, plus its JECFA cross-reference

Coverage

240 pesticides and 85 veterinary drugs, with limits indexed in both directions (by substance and by food). Pesticide limits carry their adoption year, the JMPR evaluation year, and the step code — CXL means an adopted Codex limit; a numeric step means the limit is still moving through the 8-step adoption procedure and is not yet binding.

Auth

None. Keyless, no registration, no quota.

Data sources

• Pesticide residues: https://www.fao.org/fao-who-codexalimentarius/codex-texts/dbs/pestres/en/
• Veterinary drug residues: https://www.fao.org/fao-who-codexalimentarius/codex-texts/dbs/vetdrugs/en/

No documented API. These endpoints back the site's own jQuery pages, so they are undocumented and unversioned and can drift without notice.

What is NOT here: GSFA

Codex's third database — GSFA, the General Standard for Food Additives, which is what says whether an additive is permitted in a given food and at what level — is not covered, because it is not reachable from a server. fao.org/gsfaonline sits behind a Cloudflare JavaScript challenge that returns 403 to every non-browser client, including for the standard's own PDF. This is not an IP-reputation block, so an egress proxy does not help: the SharePoint mirror requires FAO SSO, the site's own sh-proxy returns the same 403, and FAO's OpenKnowledge repository API refuses too. Reaching GSFA would need a browser-driven scrape, which is a different kind of project.

Gotchas

Four upstream behaviours produce wrong answers if trusted. All are guarded here, but they matter if you extend it:

1. About 10% of pesticide records are invalid JSON. Commodity names contain raw tab characters inside string literals — "Dry peas \t\t(subgroup)". RFC 8259 forbids unescaped U+0000–U+001F inside strings, so JSON.parse throws Bad control character in string literal and the record is simply unreachable. Sampling 30 records found 3 affected, including glyphosate. sanitizeJson() escapes control characters inside strings only, tracking in-string state, because tabs and newlines between tokens are legal whitespace that must be left alone.

2. A search that matches nothing returns the search form, not an empty list. Ask for a commodity that doesn't exist and you get back {forms: {...}} describing the search UI. Code that looks for commodities and finds nothing can easily report "no limits apply" — a confident wrong answer. isEmptySearchResponse() distinguishes the two shapes.

3. Unknown ids answer HTTP 500, not 404. So a bad id is indistinguishable from the upstream being down. Both codex_pesticide_mrls and codex_vetdrug_mrls resolve their argument against the catalogue first and never probe a detail endpoint with an id they haven't seen.

4. Absence and zero are different, and both are meaningful.

   • Zero limits is a finding: chloramphenicol returns count: 0 because Codex declines to set any MRL for a substance it judges to have no safe residue level. Reporting that as "no data" inverts the meaning.
   • A missing substance is also a finding: this database lists only currently adopted limits, and Codex removes entries when it revokes them. Chlorpyrifos is absent for exactly that reason — verified against upstream's own search, which likewise returns nothing. So absence is not evidence a substance was never evaluated, and the no_match hints say so.

Quick Start

Add to your MCP client (Claude Desktop, Cursor, Windsurf, etc.):

{
  "mcpServers": {
    "codex-mrl": {
      "url": "https://gateway.pipeworx.io/codex-mrl/mcp"
    }
  }
}

What this endpoint actually serves

tools/list at https://gateway.pipeworx.io/codex-mrl/mcp returns the tools in the table above plus the shared Pipeworx meta-tools — ask_pipeworx, discover_tools, search_within, remember/recall and the rest of the gateway-wide set. So the tool count you see is larger than this table: a single-pack endpoint currently lists roughly 30 shared tools alongside the pack's own. The connection's initialize response states its exact scope, and is the authoritative answer for a given day.

This is deliberate, not multiplexing by accident. The meta-tools are what let a scoped connection answer a question this pack does not cover — via ask_pipeworx, which routes across the whole catalog — without you adding a second MCP server. There is currently no way to mount a pack endpoint without them; if the extra schemas cost you more context than the routing is worth, connect to the full gateway once rather than to several pack endpoints.

Or connect to the full Pipeworx gateway to get every pack's tools listed directly, instead of just this one's:

{
  "mcpServers": {
    "pipeworx": {
      "url": "https://gateway.pipeworx.io/mcp"
    }
  }
}

Both URLs reach the same gateway and the same 1573+ data sources. The only difference is which pack's tools are listed directly; ask_pipeworx reaches all of them from either one.

Standalone (no gateway account)

This package also runs as a local stdio MCP server — no Pipeworx account, no gateway round-trip:

{
  "mcpServers": {
    "codex-mrl": {
      "command": "npx",
      "args": ["-y", "@pipeworx/mcp-codex-mrl"]
    }
  }
}

Or run it directly to confirm it starts:

npx -y @pipeworx/mcp-codex-mrl

It speaks MCP over stdin/stdout and answers initialize/tools/list/tools/call for only this pack's tools — none of the shared meta-tools the gateway connection above adds. Same source, same tools, no ask_pipeworx routing.

Using with ask_pipeworx

Instead of calling tools directly, you can ask questions in plain English — this works on the pack endpoint above as well as on the full gateway:

ask_pipeworx({ question: "your question about Codex Mrl data" })

The gateway picks the right tool and fills the arguments automatically.

More

• Docs and guides
• pipeworx.io

License

MIT