json-structures-and-mappings

A Mendix reference for describing JSON data and connecting it to domain entities. JSON is a text format commonly used for data sent by web APIs and message queues.

In plain words
What is it for?
Use it when turning API or queue payloads into Mendix objects, defining JSON structures, or exporting Mendix objects as JSON.
Why use it?
It helps keep incoming and outgoing data mappings consistent, including field names, arrays, nested objects, and displayed names.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/mendixlabs/mxcli/json-structures-and-mappings
Any agent
npx skills add mendixlabs/mxcli --skill json-structures-and-mappings
Clone the repo
git clone --depth 1 https://github.com/mendixlabs/mxcli

Made for: Claude Code, Codex.

Per session 53 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,056 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00053 $0.05056
Opus 5 $0.00026 $0.02528
Sonnet 5 $0.00011 $0.01011
Haiku 4.5 $0.00005 $0.00506

Measured 2d ago against content hash 1ccffff35386, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

json-structures-and-mappings scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/skills/mendix/json-structures-and-mappings/SKILL.md · 626 lines

How it starts

The opening of the file, as written. The whole thing — 626 lines — stays where its author put it; the contents beside it link to each section on GitHub.

JSON Structures, Import Mappings & Export Mappings

This skill covers creating and managing JSON structures, import mappings, and export mappings in Mendix using MDL.

Key Concepts

JSON Structures

A JSON structure defines the schema of a JSON payload. It stores a JSON snippet and auto-derives an element tree with paths, types, and custom names.

Import Mappings

An import mapping converts a JSON string into Mendix entity objects. It maps JSON fields to entity attributes.

Two names per member: the raw key and the exposed name

Every JSON structure element stores both, and for any lowercase-initial key they differ:

Example Used for
Path (raw JSON key) (Object)|uuid what the runtime resolves by
ExposedName (derived) Uuid what Studio Pro displays

Mendix derives the exposed name by capitalising the initial, and for an array's item object by suffixing Item — so totalTotal, camelCaseCamelCase, __Value (array) → __ValueItem (its item). Keys already starting with an underscore are left alone: __returnedCount stays __returnedCount.

This is Mendix's own convention, not something mxcli does. A blank app's Studio-Pro-authored FeedbackModule.JSON_AppInsightsResponse stores ExposedName: "Uuid" against Path: "(Object)|uuid", and its IMM_PostResponse binds JsonPath: "(Object)|uuid".

Consequences worth knowing:

  • Either spelling works in MDL. Total = total and Total = Total produce the same stored mapping. Write whichever you have.
  • DESCRIBE emits the raw JSON key, so its output reproduces the script that produced the mapping — Total = total comes back as Total = total, and an array binding as = item rather than = ItemItem. It also emits create or modify, so the output re-runs against the project it was read from. (Until #915 it printed the exposed name and a bare create: the text differed from the input, making every script-vs-describe diff noise, and re-running it failed with "import mapping already exists". The stored mapping was correct either way.)
  • A member matching neither spelling is refused, listing what would have worked. It is never written with a guessed path: such a mapping passed mxcli check and failed later in mxbuild (CE5015) or at runtime.

Read the full file on GitHub · 626 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 626 lines · 53 tokens per session scan A 1ccffff35386

Subscribe to this mod's changes

json-structures-and-mappings is a skill published in the GitHub repository mendixlabs/mxcli (115 stars, last pushed 3d ago), licensed Apache-2.0. It adds 53 tokens to every session and 5,056 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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