MCP tool schemas

Turn each assigned service into one MCP tool with a schema derived from its input and output.

Each service assigned to an MCP gateway becomes one tool, and everything an AI agent learns about it through tools/list comes from the service itself - there is no separate tool definition to write or keep in sync.

Tool element	Where it comes from
`name`	The service's name, e.g. `billing.get-invoice`
`description`	The service's docstring - this is what the agent's model reads when deciding which tool to call, so write docstrings for the model as much as for colleagues
`inputSchema`	Generated from the service's declared input
`outputSchema`	Generated from the service's declared output

Input schema generation

Both I/O styles produce the same JSON Schema. With plain declarations, each element maps to its JSON Schema type - Int becomes integer, Bool becomes boolean, Float becomes number, Dict becomes object, List becomes array, Date, DateTime and UUID become strings with their format, and text-like elements become strings:

class GetInvoice(Service):
    """ Returns one invoice by its ID, optionally with line items.
    """
    input = 'invoice_id', '-include_items'

With dataclass models, each field's Python annotation maps the same way - str, int, float, bool, list[T] with its element type, dict, dates, Decimal, UUID - and nested dataclasses recurse into nested object schemas. A field is required unless it has a default or its type is optional, and required names are listed in the schema's required list. In plain declarations the - prefix marks an element optional.

The generated schema is exactly what argument validation enforces when it is on - the schema agents see and the schema calls are checked against are always the same one.

A service with no declared input produces a schema that accepts any arguments.

Exposed services

Only services assigned to the gateway appear - the Services picker on the wizard's step 01 lists what can be assigned.
Internal services - names starting with zato. or pub.zato. - are never exposed, regardless of the assignment. The picker does not offer them, and the runtime refuses them even if configuration were to name them.
Tools are listed in a deterministic alphabetical order, so clients can cache the list.

Live updates

Hot-deploying a changed service rebuilds the tool list of every gateway that exposes it - the next tools/list already advertises the schemas the redeployed code declares, with no restarts. Editing the gateway itself rebuilds its registry the same way.

The Export document described under sharing a gateway with clients uses the same schema generation.

Feature	What it does
Argument validation	Checks tools/call arguments against the same generated schema
Sharing with clients	Exports the tool list with its schemas as one server.json document
MCP gateways	Configuration, endpoint behavior and the governance controls
Tool selection	Docstrings and schemas that steer agents to the right tool