MLB Signal Emitter

Table of Contents

• Example
• Workflow
• Common Patterns
• Guardrails
• Quick Reference

Example

Scenario: mlb-player-analyzer has computed a daily_quality signal for Junior Caminero on 2026-04-17 and wants to persist it.

Inputs passed to this skill:

• type: player
• date: 2026-04-17
• emitted_by: mlb-player-analyzer
• variant_synthesis: true, variants_fired: [advocate, critic]
• Body contains: form_score: 68, matchup_score: 74, opportunity_score: 62, daily_quality: 69, regression_index: +18, confidence: 0.78
• source_urls: [baseballsavant..., fangraphs..., mlb.com/gameday...]

Validation pass (what this skill checks):

Action: Write to yahoo-mlb/signals/2026-04-17-player-caminero.md and return the absolute path.

Failure scenario: If confidence: 1.4 had been passed, validation fails. The skill does NOT write the file. It calls mlb-decision-logger with a failure entry: kind: signal_validation_failure, signal_type: player, reason: confidence out of range (1.4 not in [0.0, 1.0]), emitter: mlb-player-analyzer, and returns an error to the calling agent.

Workflow

Copy this checklist and track progress:

Signal Emission Progress:
- [ ] Step 1: Receive signal payload from upstream skill/agent
- [ ] Step 2: Validate YAML frontmatter (required fields)
- [ ] Step 3: Range-check all numeric signals
- [ ] Step 4: Validate variant synthesis metadata
- [ ] Step 5: Determine and validate file path
- [ ] Step 6: Write file OR log validation failure

Step 1: Receive signal payload

The caller hands in three things: (1) YAML frontmatter key-value pairs, (2) signal body (markdown tables), (3) intent (e.g., "this is a final synthesized signal" vs. "this is an intermediate variant dump"). See resources/template.md for the canonical input shape.

• Frontmatter fields collected
• Body (markdown tables) supplied
• Intent known: final vs. variant-intermediate

Step 2: Validate YAML frontmatter

Confirm all required keys are present and well-typed. See resources/methodology.md for the full list.

• type present and in the allowed enum (lineup, waivers, streaming, trade, category-plan, playoff-push, player, matchup, regression, two-start, closer, faab, cat-state)
• date present and formatted YYYY-MM-DD
• emitted_by present and references a known skill or agent
• confidence present as a float in [0.0, 1.0]
• source_urls present as a non-empty list of URLs

Step 3: Range-check numeric signals

Every numeric signal in the body must fall inside its declared range. See resources/methodology.md for the per-signal range table (it mirrors signal-framework.md).

• Unipolar signals (form_score, matchup_score, opportunity_score, daily_quality, qs_probability, streamability_score, role_certainty, cat_pressure, playoff_matchup_quality, etc.) in [0, 100]
• Bipolar signals (regression_index, positional_flex_delta) in [-100, +100]
• Integer signals (playoff_games) >= 0
• Dollar signals (acquisition_value, faab_max_bid, faab_rec_bid) >= 0
• Enum signals (cat_position, verdict) inside their declared allowed sets

Step 4: Validate variant synthesis metadata

If this is a synthesized final signal, it must declare which variants produced it.

• If variant_synthesis: true, variants_fired is a list with >= 1 entry
• If variant_synthesis: true, synthesis_confidence is present and in [0.0, 1.0]
• If variant_synthesis: false, the file is an intermediate variant dump; filename must include the variant suffix (see Step 5)
• red_team_findings (if present) is a list of objects with severity, likelihood, score, note fields

Step 5: Determine and validate file path

The canonical path is yahoo-mlb/signals/YYYY-MM-DD-<type>.md. For an intermediate variant dump, use YYYY-MM-DD-<type>-<variant>.md. For per-player or per-game files, an optional identifier suffix is allowed: YYYY-MM-DD-<type>-<identifier>.md.

• Compute path from date and type in frontmatter
• Check that a signal of this type+date does not already exist unless the caller explicitly passed overwrite: true
• Ensure the parent directory exists (create if missing)
• Reject paths that escape the signals/ directory

Step 6: Write file OR log validation failure

If all checks pass: write the file, return the absolute path. If any check fails: do NOT write, call mlb-decision-logger with a structured failure entry, return an error object to the caller. See resources/methodology.md for the failure log schema.

• On pass: write file, return absolute path
• On fail: build failure object (reason, field, expected, actual), send to mlb-decision-logger, return error

Common Patterns

Pattern 1: Per-player daily signal (type: player)

• Filename: YYYY-MM-DD-player-<lastname>.md (e.g., 2026-04-17-player-caminero.md)
• Required numeric signals in body: daily_quality, plus the three components (form_score, matchup_score, opportunity_score)
• Always a final synthesized signal when emitted by mlb-player-analyzer -- so variant_synthesis: true and variants_fired: [advocate, critic]
• Source URLs must include Baseball Savant, FanGraphs, and MLB.com (confirmed lineup)

Pattern 2: Daily lineup roll-up (type: lineup)

• Filename: YYYY-MM-DD-lineup.md
• Body references, by name, the per-player signal files it consumed (provenance chain)
• synthesis_confidence reflects agreement between the advocate (bat-everyone) and critic (sit-risky) variants
• Red-team findings typically flag weather, role uncertainty, or fragile platoon calls

Pattern 3: Intermediate variant dump (variant suffix in filename)

• Filename: YYYY-MM-DD-<type>-advocate.md or YYYY-MM-DD-<type>-critic.md
• variant_synthesis: false (this IS a variant, not a synthesis)
• emitted_by names the agent and variant (e.g., mlb-lineup-optimizer/advocate)
• The synthesizing agent reads these two intermediate files, produces the final synthesized signal, then emits with variant_synthesis: true

Pattern 4: Low-confidence graceful degrade

• When a web search fails, the upstream skill should still emit a signal but with confidence <= 0.3 and a red_team_findings entry flagging the missing data source
• This skill does NOT reject low-confidence signals -- low confidence is legitimate. It only rejects out-of-range or missing fields.
• Flag in body: "Could not verify opposing pitcher; using prior-start proxy."

Guardrails

1. Never silently drop a signal. If validation fails, the failure must be logged via mlb-decision-logger so the calibration review can see what was rejected and why. A signal that never gets written AND never gets logged is invisible to the team.

2. Do not re-derive signal values. This skill is a validator and file-writer only. It never computes daily_quality or any other signal itself. If an upstream skill passes in a half-computed signal, reject it rather than filling in the blanks.

3. Reject unknown type values. The enum in signal-framework.md is the authoritative list. If a caller passes type: vibe-check, reject and log. Adding a new signal type requires updating signal-framework.md first, then this skill's validator.

4. Range checks are hard limits. A form_score of 105 is not "close enough" -- it indicates a bug upstream (probably forgot to normalize). Reject and log. Do NOT clamp-and-accept.

5. confidence is required, not optional. Even a perfectly-computed signal with three source URLs must carry a confidence float. A missing confidence is a validator failure, not a warning.

6. source_urls must be a non-empty list. Per CLAUDE.md rule 1 ("Web-search everything"), every factual signal is backed by a live source. An empty source_urls list means the signal was not grounded -- reject and log.

7. Variant synthesis claims must be provable. If variant_synthesis: true but variants_fired is empty or missing, that is a lie about the team's process. Reject and log.

8. Do not overwrite without explicit consent. If a signal already exists at the target path, refuse to overwrite unless the caller passes overwrite: true. This prevents losing an earlier morning's signal when a mid-day re-run happens.

Quick Reference

Required frontmatter fields (always):

• type (enum)
• date (YYYY-MM-DD)
• emitted_by (string)
• confidence (float 0.0-1.0)
• source_urls (non-empty list)

Required when variant_synthesis: true:

• variants_fired (list, >= 1)
• synthesis_confidence (float 0.0-1.0)

File path conventions:

• Final synthesized: signals/YYYY-MM-DD-<type>.md
• With identifier: signals/YYYY-MM-DD-<type>-<id>.md
• Intermediate variant: signals/YYYY-MM-DD-<type>-<variant>.md

Signal ranges (see resources/methodology.md for the full table):

• Unipolar (0-100): form_score, matchup_score, opportunity_score, daily_quality, qs_probability, k_ceiling, era_whip_risk, streamability_score, role_certainty, save_role_certainty, cat_pressure, cat_reachability, cat_punt_score, positional_need_fit, opp_sp_quality, park_hitter_factor, park_pitcher_factor, weather_risk, bullpen_state, playoff_matchup_quality, holding_value, obp_contribution, sb_opportunity
• Bipolar (-100 to +100): regression_index, positional_flex_delta
• Dollar (>= 0): acquisition_value, faab_max_bid, faab_rec_bid, trade_value_delta
• Integer (>= 0): playoff_games
• Enum: cat_position (winning|tied|losing), verdict (accept|counter|reject)

On validation failure:

1. Do NOT write the signal file.
2. Build failure entry: {kind: signal_validation_failure, signal_type, reason, field, expected, actual, emitter, timestamp}.
3. Call mlb-decision-logger with the failure entry.
4. Return an error object to the caller.

Key resources:

• resources/template.md: Canonical signal file template with every required frontmatter field and a fully-populated example body
• resources/methodology.md: Validation rules -- required fields, range checks, variant-synthesis checks, path conventions, failure handling
• resources/evaluators/rubric_mlb_signal_emitter.json: 8 criteria for evaluating the emitter's behavior

Inputs required:

• Frontmatter key-value pairs from caller
• Signal body (markdown tables)
• overwrite flag (default false)

Outputs produced:

• On success: absolute file path of the written signal
• On failure: error object; a failure entry appended to tracker/decisions-log.md via mlb-decision-logger