The host package

Summary

Submodules

annotations	MCP tool annotations (behavior hints) for the leaf tool surface.
guidance	Uniform retryable / next_action guidance on tool error results.
operations	Make long-running mutating tool calls survive host timeouts.
trace	Per-call trace ids so host-side and server-side logs line up.

Classes

HostContract

Wrap tool functions with trace ids, timeout-safe execution and error guidance.

Functions

annotations_for	Return the behavior hints for a tool.
error_guidance	Classify an error code.
current_trace_id	Return the trace id of the tool call running in this context.
host_contract_enabled	Return whether the host contract should wrap tools.

Constants

HOST_CONTRACT_ENV

Environment variable that turns the host contract off when set to 0.

Description

Host-facing contract for generic MCP hosts.

Generic MCP hosts (VS Code Copilot, Claude Desktop, Cursor) rely on:

• behavior hints on every tool (ansys.fluent.mcp.common.host.annotations);

• retryable / next_action guidance on error results (ansys.fluent.mcp.common.host.guidance);

• long-running mutating calls that survive host timeouts (ansys.fluent.mcp.common.host.operations);

• per-call trace ids in the server log (ansys.fluent.mcp.common.host.trace).

HostContract applies all of this by wrapping each tool function at registration time. It uses only the standard library, so this package does not depend on the internals of the MCP server framework. Set FLUIDS_MCP_HOST_CONTRACT=0 to turn it off.

Module detail

host.host_contract_enabled() → bool

Return whether the host contract should wrap tools.

Returns:

bool

False only when FLUIDS_MCP_HOST_CONTRACT is a falsy value.

host.HOST_CONTRACT_ENV = 'FLUIDS_MCP_HOST_CONTRACT'

Environment variable that turns the host contract off when set to 0.