awesome-copilot/plugins/phoenix/skills/phoenix-cli/references/axial-coding.md

Axial Coding

Group open-ended observations into structured failure taxonomies. Axial coding turns notes, trace observations, or open-coding output into named categories with counts, supporting downstream work like eval design and fix prioritization. It works well after open coding, but can start from any set of open-ended observations.

Reach for this whenever the user has observations and needs structure — e.g., "what categories of failures do we have", "what should I build evals for", "how do I prioritize fixes", "group these notes", "MECE breakdown", or any framing that asks for categories or counts grounded in real traces rather than invented top-down.

Choosing the unit

Open-coding notes are usually trace-level (see open-coding.md#choosing-the-unit) — examples below lead with px trace and fall back to px span for span-level notes. An axial label can live at a different level than the note that informed it — that's a feature: a trace-level note "answered shipping when asked returns" can produce a span-level annotation on the retrieval span once a pattern reveals retrieval as the consistent culprit. Re-attribution at axial coding time is what axial coding is. Session-level rollups go through REST /v1/projects/{id}/session_annotations (no CLI write path).

Process

1. Gather — Collect open-coding notes from the entities you reviewed (trace-level by default)
2. Pattern — Group notes with common themes
3. Name — Create actionable category names
4. Attribute — Decide what level each category lives at; an axial label can move from the note's level to the component the pattern implicates
5. Quantify — Count failures per category

Example Taxonomy

failure_taxonomy:
  content_quality:
    hallucination: [invented_facts, fictional_citations]
    incompleteness: [partial_answer, missing_key_info]
    inaccuracy: [wrong_numbers, wrong_dates]

  communication:
    tone_mismatch: [too_casual, too_formal]
    clarity: [ambiguous, jargon_heavy]

  context:
    user_context: [ignored_preferences, misunderstood_intent]
    retrieved_context: [ignored_documents, wrong_context]

  safety:
    missing_disclaimers: [legal, medical, financial]

Reading

1. Gather — extract open-coding notes

Open-coding notes are stored as annotations with name="note" and are only returned when --include-notes is passed. Use --include-annotations instead and you will get structured annotations but not notes — the server excludes notes from the annotations array.

# Trace-level notes (default for open coding)
px trace list --include-notes --format raw --no-progress | jq '
  [ .[] | select((.notes // []) | length > 0) ]
  | map({ trace_id: .traceId, notes: [ .notes[].result.explanation ] })
'

# Span-level notes (when open coding dropped to span for mechanical failures)
px span list --include-notes --format raw --no-progress | jq '
  [ .[] | select((.notes // []) | length > 0) ]
  | map({ span_id: .context.span_id, notes: [ .notes[].result.explanation ] })
'

2. Group — synthesize categories

Review the note text collected above. Manually identify recurring themes and draft candidate category names. Aim for MECE coverage: each note should fit exactly one category.

3. Record — write axial-coding annotations

Write one annotation per entity using px trace annotate or px span annotate. The level can differ from where the source note lives — see the Recording section below.

4. Quantify — count per category

After recording, use --include-annotations to count how many entities carry each label. Examples below show span-level counts; for trace-level annotations, swap px span list for px trace list (the .annotations[] shape is the same).

px span list --include-annotations --format raw --no-progress | jq '
  [ .[] | .annotations[]? | select(.name == "failure_category" and .result.label != null) ]
  | group_by(.result.label)
  | map({ label: .[0].result.label, count: length })
  | sort_by(-.count)
'

Filter to a specific annotation name to check coverage:

px span list --include-annotations --format raw --no-progress | jq '
  [ .[] | select((.annotations // []) | any(.name == "failure_category")) ]
  | length
'

Recording

Use the matching annotate command for the level the label belongs at — which may differ from where the source note lives (see Choosing the unit):

# Trace-level label (most common — the trace as a whole exhibits the failure)
px trace annotate <trace-id> \
  --name failure_category \
  --label answered_off_topic \
  --explanation "asked about returns; answer covered shipping" \
  --annotator-kind HUMAN

# Span-level label (when the pattern implicates a specific component)
px span annotate <span-id> \
  --name failure_category \
  --label retrieval_off_topic \
  --explanation "retrieved shipping docs for a returns query" \
  --annotator-kind HUMAN

Accepted flags: --name, --label, --score, --explanation, --annotator-kind (HUMAN, LLM, CODE). There are no --identifier or --sync flags on these commands.

Bulk recording

Axial coding categorizes the entities you took notes on during open coding. Do not filter by --status-code ERROR — that captures only spans where Python raised, which excludes most failure modes (hallucination, wrong tone, retrieval miss). See open-coding.md for the full reasoning.

# Bulk-annotate traces that already have open-coding notes
px trace list --include-notes --format raw --no-progress \
  | jq -r '.[] | select((.notes // []) | length > 0) | .traceId' \
  | while read tid; do
      px trace annotate "$tid" \
        --name failure_category \
        --label answered_off_topic \
        --annotator-kind HUMAN
    done

The same pattern works for span-level notes — swap px trace for px span and .traceId for .context.span_id.

Aside: for Node-based bulk scripts, @arizeai/phoenix-client exposes addSpanAnnotation, addSpanNote, and addTraceNote. (No addTraceAnnotation is exported today; use the REST endpoint or px trace annotate for trace-level annotations.)

Aside: px api graphql rejects mutations — it cannot write annotations.

Agent Failure Taxonomy

agent_failures:
  planning: [wrong_plan, incomplete_plan]
  tool_selection: [wrong_tool, missed_tool, unnecessary_call]
  tool_execution: [wrong_parameters, type_error]
  state_management: [lost_context, stuck_in_loop]
  error_recovery: [no_fallback, wrong_fallback]

Transition Matrix — jq sketch

To find where failures occur between agent states, identify the last non-error span before each first-error span within a trace. Note: OTel leaves most spans at status_code == "UNSET" and only sets "OK" when code explicitly does so — match != "ERROR" rather than == "OK" so the matrix works on typical OTel data.

px span list --format raw --no-progress | jq '
  group_by(.context.trace_id)
  | map(
      sort_by(.start_time)
      | { trace_id: .[0].context.trace_id,
          last_non_error: map(select(.status_code != "ERROR")) | last | .name,
          first_err:      map(select(.status_code == "ERROR")) | first | .name }
    )
  | [ .[] | select(.first_err != null) ]
  | group_by([.last_non_error, .first_err])
  | map({ transition: "\(.[0].last_non_error) → \(.[0].first_err)", count: length })
  | sort_by(-.count)
'

Use the output to tally which state-to-state transitions are most failure-prone and add them to your taxonomy.

What Makes a Good Category

A useful category is:

• Named for the cause, not the symptom ("wrong_tool_selected", not "bad_output")
• Tied to a fix — if you can't name a remediation, the category is too vague
• Grounded in data — emerged from actual note text, not assumed upfront

Principles

• MECE - Each failure fits ONE category
• Actionable - Categories suggest fixes
• Bottom-up - Let categories emerge from data