Output Schemas for Clients
Publish the shape so consumers can rely on it.
Output Schemas for Clients is a free MCP Academy lesson on CoddyKit — lesson 3 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the MCP Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Publish the Shape
A structured tool can also advertise an output schema: a JSON Schema that tells clients exactly what fields and types to expect.
What an Output Schema Is
It is a machine-readable description of your result, listing each field name and its type. Clients read it before ever calling the tool.
Generated From Your Model
When you return a Pydantic model, the SDK derives the output schema for you. Your type hints become the published contract automatically.
Where Clients See It
The schema rides along in the tool listing under outputSchema. A client inspecting tools learns the shape without trial and error.
{"type": "object", "properties": {"temp_c": {"type": "number"}}}Why Clients Want It
With a known schema, a client can validate results and build UI ahead of time. There is no guessing about which fields will appear.
Types Carry Meaning
The schema marks temp_c as a number and condition as a string. Consumers trust these types instead of inferring them from one sample.
Required vs Optional
Fields with defaults become optional in the schema; others are required. Clients learn which keys are guaranteed to be present.
class Weather(BaseModel):
temp_c: float
note: str = ""A Stable Contract
Treat the output schema like a promise. Once clients depend on it, changing field names or types can break them downstream.
Schemas Aid Validation
Strict clients validate every result against the schema and reject mismatches. This catches server bugs fast, right at the boundary.
Self-Documenting Tools
An output schema doubles as documentation. New developers read the schema to understand a tool without digging through your code.
Keep Schemas Honest
Make sure your tool always returns what the schema claims. A result that drifts from its schema erodes the trust clients place in it.
Quick Check
Where does a tool publish the shape of its result?
Recap: Output Schemas
You saw how a tool publishes an output schema from your model. It documents fields, enables validation, and forms a stable contract. ✅
Frequently asked questions
Is the “Output Schemas for Clients” lesson free?
Yes — the full text of “Output Schemas for Clients” is free to read here on the web, and the MCP Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the MCP Academy course, upgrade to CoddyKit PRO.
What will I learn in “Output Schemas for Clients”?
Publish the shape so consumers can rely on it. You practise MCP Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start MCP Academy?
No prior experience is required. MCP Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Output Schemas for Clients” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this MCP Academy lesson?
Yes. Every MCP Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Text vs Structured Content
- Return a Typed Result Object
- Output Schemas for Clients
- Return Images & Binary Blobs