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POST
Node.js
See the WebMCP guide for SDK examples and invocation lifecycle details.

Authorizations

x-api-key
string
header
required

Path Parameters

id
string<uuid>
required

Session ID.

Body

application/json
toolRef
string
required
Required string length: 1 - 4096
input
object

Arguments matching the tool inputSchema. At most 1 MiB when JSON encoded. Keys are passed through unchanged.

timeoutSeconds
integer
default:300

Tool execution budget in seconds. Expiration requests cancellation; it does not guarantee rollback.

Required range: 1 <= x <= 3600

Response

Invocation accepted

Ephemeral, session-local handle. Pending states have no result or error. A terminal handle may contain a result or an error. Lost on receiver restart, session rebind, or browser shutdown. At most 16 active and 64 retained; terminal results expire after 10 minutes and may be evicted sooner.

invocationId
string
required
Pattern: ^[a-f0-9]{24}$
toolRef
string
required
status
enum<string>
required
Available options:
running,
awaiting_submission,
completed,
error,
canceled,
outcome_unknown
cancellationRequested
boolean
required

Whether cancellation was requested, regardless of the final outcome.

createdAt
string<date-time>
required
expiresAt
string<date-time>

Nominal terminal-result expiry. Results may be evicted earlier.

result
object
error
object