> ## Documentation Index > Fetch the complete documentation index at: https://sdk.umbraprivacy.com/llms.txt > Use this file to discover all available pages before exploring further. # Tree Metadata > Returns metadata for a specific Indexed Merkle Tree: leaf count, current root hash, and Stealth Pool Note record count. The root hash changes every time a new leaf is inserted. Use this endpoint to check the current state of a tree before fetching notes or generating Merkle proofs. `utxo_count` may differ from `num_leaves` if some leaves were inserted without Stealth Pool Note ciphertext data (e.g. padding leaves). ## OpenAPI ````yaml GET /v1/trees/{tree_index} openapi: 3.0.3 info: title: Umbra Indexer Read Service description: > Read-only REST API for querying Umbra mixer tree state, UTXO records, and Merkle inclusion proofs. ## Response Encoding **All endpoints** support `application/x-protobuf` encoding. The encoding strategy differs by endpoint category: - **Always Protobuf** (no content negotiation): stats, tree metadata, Merkle proofs, and all UTXO data endpoints. These endpoints always respond with `Content-Type: application/x-protobuf` regardless of the `Accept` header. - **Content negotiation** (health endpoints only): respond with JSON by default, or Protobuf when `Accept: application/x-protobuf` is set. Send `Accept: application/x-protobuf` for consistent protobuf-only clients. ## UTXO Response Layouts The three UTXO data endpoints (`GET /v1/utxos`, `GET /v1/utxos/{absolute_index}`, `GET /v1/trees/{tree_index}/utxos`) support two Protobuf response layouts controlled by the `X-Response-Layout` request header: - **Row-oriented** (default) -- `UtxoResponse` message: each UTXO is a self-contained `UtxoDataItem` sub-message. Easier to iterate record-by-record. - **Columnar** (`X-Response-Layout: columnar`) -- `UtxoColumnarResponse` message: each field across all UTXOs is packed into a parallel array inside a single `UtxoColumns` sub-message. Compresses significantly better over the wire and is preferred by vectorized consumers (e.g. data pipelines, analytics). ## Rate Limiting All endpoints are subject to rate limiting. Exceeded limits return `429 Too Many Requests`. ## Compression All responses are compressed. Send `Accept-Encoding: gzip, br`. ## Absolute Index The **absolute index** is a globally monotonic cursor across all Merkle trees: ``` absolute_index = tree_index * MAX_LEAVES_PER_TREE + insertion_index ``` where `MAX_LEAVES_PER_TREE = 1,048,576` (2^20). version: 0.1.0 contact: name: Umbra Protocol servers: - url: https://utxo-indexer.api.umbraprivacy.com description: Mainnet - url: https://utxo-indexer.api-devnet.umbraprivacy.com description: Devnet security: [] tags: - name: health description: | Health and readiness probes for Kubernetes or load-balancer checks. Support both JSON and Protobuf via `Accept` header negotiation. - name: stats description: Aggregate statistics for the UTXO index. Always Protobuf. - name: trees description: Per-tree Merkle metadata and Merkle inclusion proofs. Always Protobuf. - name: utxos description: > UTXO data queries with absolute-index-based pagination. Always Protobuf. Supports row-oriented and columnar response layouts via `X-Response-Layout`. paths: /v1/trees/{tree_index}: get: tags: - trees summary: Merkle tree metadata description: > Returns metadata for a specific Indexed Merkle Tree: - `num_leaves` -- current leaf count. - `root` -- current Poseidon root hash (raw bytes). - `utxo_count` -- UTXO records stored for this tree. **Always Protobuf** -- responds with `application/x-protobuf` regardless of the `Accept` header. **Tree capacity**: `MAX_LEAVES_PER_TREE = 1,048,576` (depth-20 tree). Once full, the write service starts a new tree at the next sequential index. operationId: getTreeInfo parameters: - name: tree_index in: path required: true description: Zero-based index of the Merkle tree to query. schema: type: integer format: int64 minimum: 0 example: 0 responses: '200': description: Tree metadata retrieved successfully. content: application/x-protobuf: schema: $ref: '#/components/schemas/TreeInfoResponse' '400': description: Invalid `tree_index` parameter. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '404': description: No tree with the specified index exists. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '429': description: Rate limit exceeded. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '500': description: Storage backend error. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' components: schemas: TreeInfoResponse: type: object description: > Protobuf `TreeInfoResponse` message returned by `GET /v1/trees/{tree_index}`. The `root` field is a `bytes` field in the Protobuf encoding containing the raw 32-byte little-endian Poseidon root hash. **Tree capacity**: Each tree holds at most `MAX_LEAVES_PER_TREE = 1,048,576` leaves (depth-20 Indexed Merkle Tree). required: - tree_index - num_leaves - root - utxo_count properties: tree_index: type: integer format: int64 description: Zero-based index identifying the Merkle tree. example: 0 num_leaves: type: integer format: int64 description: Total number of leaf commitments currently inserted into the tree. example: 1024 root: type: string format: byte description: > Raw 32-byte little-endian Poseidon root hash (Protobuf `bytes` field). In a JSON representation this would be base64-encoded. example: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA= utxo_count: type: integer format: int64 description: Number of UTXO records stored for this tree in the UTXO store. example: 1024 ErrorResponse: type: object description: Standard JSON error body returned on 4xx and 5xx responses. required: - error - message properties: error: type: string description: | Short error category, e.g. `"Bad Request"`, `"Not Found"`, `"Too Many Requests"`, `"Internal Server Error"`. example: Not Found message: type: string description: Human-readable explanation of what went wrong. example: Tree 99 not found ````