MCP tools reference

Your assistant gets five tools and picks between them on its own. You never call these by hand — this page is here so you know what it can reach for.

Tool	What your assistant does with it
`read`	Fetch one thing by id, name, or `opik://` URI.
`list`	Page through many, with filters, sorting and a time window.
`write`	Create and annotate: traces, spans, scores, comments, prompt versions, test suites, experiments.
`schema`	Look up the exact payload shape for a write, or the filter and sort vocabulary for a list.
`read_skill`	Load one of the Opik skills on demand, when the skill pack isn’t installed in the client.

What it can read

read fetches a single entity, and several come with their children inlined, so one call is usually enough:

Entity	What comes back
`trace`	The trace plus its span tree
`span`	One span
`thread`	The thread plus its messages
`prompt`	The prompt plus its versions
`project`, `experiment`, `test_suite`	The entity itself
Diagnostics issue	The issue, its details, and example trace ids

project, experiment, prompt and test_suite can be fetched by name as well as by id, so your assistant doesn’t need a UUID to get started. Traces, spans and threads can be pasted in as an Opik URL.

list covers those plus test suite items and prompt versions. Traces, spans, threads and experiments also support filtering and sorting — by name, status, feedback score, token usage, duration or time window — which is how your assistant answers “the slowest failing traces from yesterday” in one call.

What it can write

One tool, write, covers every change:

Area	Operations
Tracing	Create and update traces, create spans
Annotation	Attach feedback scores and comments to a trace, span or thread
Prompts	Save a new prompt version
Evaluation	Create test suites and upsert their items; create experiments and experiment items
Threads	Open and close a thread
Diagnostics	Enable or trigger a scan; resolve, close or reopen an issue

Nothing can be deleted. There is no delete operation in the tool surface, on any entity. write also accepts a dry_run flag, which validates a payload and your permissions without sending anything to your workspace.

The skills that ship with it

Running an evaluation end to end is a skill’s job, not a tool’s: the skills drive the Opik SDK, and the MCP tools record and read the results. That is why uvx opik mcp configure installs both. Your assistant picks between them the same way it picks tools:

Skill	When it reaches for it
`opik-instrument`	”add Opik tracing”, “instrument my code”, “trace my agent”
`opik-evaluate`	Measuring or improving quality — evals, judges, metrics
`opik-diagnose`	”what is broken in production”, “triage my agent”
`opik-explain`	”why did this trace fail”, “why is my agent slow”
`opik`	SDK reference lookups: span types, metadata, flushing, prompt versioning

Looking at a payload yourself

Ask your assistant “show me the schema for trace.create” and it will call schema and show you the JSON Schema and an example. The server’s README lists every operation name.