eLabFTW MCP

update_entity_metadata

Update custom metadata fields on eLabFTW experiments, items, templates or item types. Merge new fields with existing metadata or overwrite it completely.

Instructions

Update the metadata (custom fields) of an eLabFTW experiment, item, experiment template or item type. WRITE OPERATION — requires the update write scope. 'fields' is a JSON string with an array of field objects ({key, value | values, type, group_id, allow_multi_values, description}); 'groups' optionally defines extra field groups ([{id, name}]). mode='merge' (default) keeps the existing metadata, 'overwrite' rebuilds it from the supplied fields. Returns the resulting field names and a read-back verification.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "entity_type": "<entity_type>",
      "id": "<id>",
      "fields": "<fields>"
    },
    "name": "update_entity_metadata"
  }
}

Input Schema

Name	Required	Default
`id`	Yes
`mode`	No	merge
`fields`	Yes
`groups`	No
`trace_id`	No
`entity_type`	Yes

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Oct 7, 2026

TDQS

A3.8/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full burden and largely meets it: it discloses the write nature, the required write scope, the destructive semantics of mode='overwrite' ('rebuilds it'), the preservation semantics of 'merge', and a read-back verification. It omits edge behavior such as what happens to fields not mentioned in a merge or any rate limits.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the purpose and the WRITE OPERATION/scope warning, then parameter detail. The 'fields' schema description is dense but every element earns its place; no filler sentences.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return values need not be spelled out, yet the description still summarizes the read-back verification. Combined with the write-scope note and mode semantics, this is nearly complete for a 6-param write tool; only the trace_id parameter and merge edge cases are unaddressed.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must compensate, and it does for the complex parameters — it gives the JSON shape of 'fields' ({key, value | values, type, group_id, allow_multi_values, description}), the structure of 'groups' ([{id, name}]), and the default/values of 'mode'. The simple params (id, entity_type) are self-evident, but 'trace_id' is left undocumented.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb ('Update') and resource ('metadata (custom fields)') and enumerates the four entity types it applies to, so the agent knows what it targets. It does not differentiate itself from the sibling 'update_entity_fields', which sounds like a near-identical operation, leaving a routing ambiguity.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explains the merge vs overwrite modes and flags 'WRITE OPERATION — requires the update write scope', which is useful operational guidance. However, it never states when to choose this tool over the sibling 'update_entity_fields', so the agent must infer the distinction.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.