CWL to MCP Crosswalk

CWL source	Extension role	MCP target
id	default tool identity	name
label	default presentation title	title
doc	base descriptive text	description
inputs	authoritative input model	inputSchema
outputs	authoritative output model	outputSchema
mcp:Tool.name	explicit override	name
mcp:Tool.title	explicit override	title
mcp:Tool.description	explicit override	description
mcp:Tool.useWhen	usage guidance	composed into description or metadata
mcp:Tool.doNotUseWhen	avoidance guidance	composed into description or metadata
mcp:Tool.aliases	discovery metadata	_meta or generator-only data
mcp:Tool.annotations.title	display fallback hint	annotations.title
mcp:Tool.annotations.*	direct hint mapping	annotations.*

Notes

• The extension is additive, not substitutive.
• CWL remains the source of truth for input/output typing.
• MCP display precedence is title, then annotations.title, then name.
• Generators may keep richer provenance metadata than is emitted into the MCP Tool object.