Schema

The envelope

Every TCPP message is one JSON object with the same five or six top-level members. The endpoint decides what goes in record; everything around it is identical whether the message reports a charging session or answers a ping.

The head

Twelve required fields. A response repeats the request's head with the direction reversed, origin and target swapped, and its own outcome in error_code.

Identifiers

Every id in a head (origin, target, context, participants) carries a one-letter prefix and a colon, naming the namespace it belongs to, so an identifier is never ambiguous about what kind of thing it names. The whole id, prefix included, is at most 120 characters.

Module types

Three upper-case letters identify what a participant is. The type says which role a party plays in the protocol; the id says which one it is.

Trusted services

Market participants

Charge points and local devices

Metering and energy management

Context types

context_type names the kind of process a message belongs to, and is drawn from a separate set: CRG charging · ENG energy control · MNT maintenance · INF information · DRR data request record · TFF tariff.

Error codes

Six hexadecimal digits, used in the head, in the per-element parsed block of a response and in references. The code is read in three parts: the first digit is the global class, the next two the detailed status, and the last three a module-specific status, FFF where the module is not identified.

So 000000 is success and FFFFFF is an unknown failure. A response that accepted the head but rejected one array element says so in parsed, keyed by the path to that element, rather than failing the whole message.

Signing

A TCPP message travels as a compact JWS with alg: ES384, ECDSA over the NIST P-384 curve with SHA-384. The JSON object above is the payload; the receiver decodes it, checks it against the sender's public key, and keeps both the message and the token it arrived in.

JWS signatures use the fixed-width R‖S encoding of IEEE P1363, which is what a browser's Web Crypto produces. Libraries that emit DER, Go's ecdsa.SignASN1 among them, need converting first, including the left-padding of a short coordinate.

A signature can also be carried inside a message: each entry in references may hold the jws of the record it refers to, so a chain of records can be handed on as one document and still be checked link by link. Note that this member is an object, not the compact string a message travels as: inside a record the signature is carried in the JSON serialisation of JWS, so that it stays readable as JSON rather than as one opaque line.

Endpoints

Twenty-seven request/response pairs. Each name below links to its two schema files.

Charging

Metering

Identity, keys and verification

Configuration

Operation

Archive

The envelope schema

all.json is the base format the others specialise: the head, the participant and reference definitions, and a free-form record. Validate against it when you need to read a message whose endpoint you do not implement.

• all.json

Getting the files

All 55 files, as served here, are also packaged as one archive. The reference node embeds the same set and serves it at the same paths, so an implementation can be developed against a local copy and moved to the published URLs unchanged.