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fix: register google-duration format to silence unknown format warnings #2601

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fix: register google-duration format to silence unknown format warnings #2601

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2ee36f6
fix: register google-duration format to silence unknown format warnings
norberto Aug 2, 2026
9e99668
chore: add changeset for google-duration format registration
norberto Aug 2, 2026
fce58bc
style: fix prettier formatting in ajvProvider.ts
norberto Aug 2, 2026
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9 changes: 9 additions & 0 deletions .changeset/register-google-duration-format.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
---
'@modelcontextprotocol/core-internal': patch
'@modelcontextprotocol/client': patch
'@modelcontextprotocol/server': patch
---

Register `google-duration` format on default AJV instances to silence "unknown format" warnings.

Firebase MCP and other Google Cloud API MCP servers use the `google-duration` format in their JSON Schemas (values like `"3600s"`, `"1.5s"`). AJV logs `unknown format "google-duration" ignored` warnings for each schema that references it, creating noisy startup output. The format is registered with a regex matching Google's Duration proto format: a number followed by a time unit suffix (`s`, `ms`, `us`, `ns`, `m`, `h`, `d`).
12 changes: 12 additions & 0 deletions packages/core-internal/src/validators/ajvProvider.ts
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Expand Up @@ -27,6 +27,13 @@ interface AjvValidateFunction {
/** `ajv-formats` default export, normalised through the CJS/ESM interop wrapper. */
const addFormats = _addFormats as unknown as typeof _addFormats.default;

/**
* Validate the `google-duration` format used by Google Cloud APIs (e.g. Firebase MCP).
* Accepts strings like "3600s", "1.5s", "100ms", "2m", "1h", "1d" — a number followed
* by a time unit suffix. See https://cloud.google.com/ruby/docs/reference/google-cloud-env/latest/Google/Protobuf/Duration
*/
const GOOGLE_DURATION_RE = /^\d+(\.\d+)?(s|ms|us|ns|m|h|d)$/;

function createDefaultAjvInstance(engineClass: typeof Ajv2020 | typeof Ajv2019 | typeof Draft7Ajv): AjvLike {
const ajv = new engineClass({
strict: false,
Expand All @@ -35,6 +42,11 @@ function createDefaultAjvInstance(engineClass: typeof Ajv2020 | typeof Ajv2019 |
allErrors: true
});
addFormats(ajv);
// Register Google Cloud duration format to silence "unknown format" warnings
// from MCP servers that use Google API schemas (e.g. Firebase MCP).
if ('addFormat' in ajv && typeof ajv.addFormat === 'function') {
(ajv as { addFormat: (name: string, format: unknown) => void }).addFormat('google-duration', GOOGLE_DURATION_RE);
}
return ajv;
}

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