Make MCP working-directory validation regex-portable - #22
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Replace the 1.1.0 `cwd` regular expression with direct `anyOf`
alternatives for the forms defined by §7.2.1. Use `const` for exact
`${PLUGIN_ROOT}` and `${PLUGIN_DATA}` values and simple prefix patterns
for rooted paths so validators do not depend on noncapturing groups or
engine-specific `$` behavior.
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Submitted as agentplugins#80. |
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Problem
The 1.1.0 MCP schema validates
cwdwith one regular expression containing noncapturing groups and$alternatives. Noncapturing groups are outside the portable regular-expression subset recommended by JSON Schema, and$has different end-of-string behavior across regular-expression engines.In particular, Python-style engines allow
$to match before a terminal newline. They therefore accept${PLUGIN_ROOT}\nand${PLUGIN_DATA}\n, although neither value has one of the forms required by §7.2.1.Resolution
Replace the single expression with
anyOfalternatives that represent the accepted forms directly:./.${PLUGIN_ROOT}.${PLUGIN_ROOT}/.${PLUGIN_DATA}.${PLUGIN_DATA}/.Use
constfor the exact placeholder values and simple start-anchored patterns for the prefix forms. This removes both noncapturing groups and end anchors while preserving thecwdlanguage defined by §7.2.1.anyOfexpresses the actual requirement: a value must have at least one accepted form. The alternatives happen to be mutually exclusive, but that is not a separate contract to enforce withoneOf.The correction applies to the 1.1.0 working draft. The published 1.0.0 schema retains its canonical contents.
Validation
schemas/1.1.0/mcp.schema.jsonas Draft 2020-12 with Ajv.Follow-up to agentplugins#79.