MLB League State Reader

Example
Workflow
Degraded Mode
Guardrails
Quick Reference

Example

Scenario: Morning brief run on 2026-04-17. Coach needs current roster, matchup, FAAB, and standings before launching lineup-optimizer.

Inputs read first:

~/Documents/Projects/yahoo-mlb/context/league-config.md (league ID 23756, team 5, 12 teams, 5x5 cats)
~/Documents/Projects/yahoo-mlb/context/team-profile.md (prior known roster skeleton)

Chrome navigation sequence (authenticated):

https://baseball.fantasysports.yahoo.com/b1/23756/5 — roster with today's opponents per player
https://baseball.fantasysports.yahoo.com/b1/23756?lhst=stand — standings + category ranks
https://baseball.fantasysports.yahoo.com/b1/23756/matchup — this week's head-to-head vs Los Doyers
https://baseball.fantasysports.yahoo.com/b1/23756/transactions — FAAB spent to date → remaining
https://baseball.fantasysports.yahoo.com/b1/23756/players?status=A — top free agents (page 1)

Extracted bundle:

Field	Value
Record	8-6-1
Rank	5 of 12
FAAB spent	$14
FAAB remaining	$86
This week opp	Los Doyers
Live matchup score	4-3-3 (us leading R, HR, K; losing OBP, ERA, WHIP)
Roster returned	26 of 26 slots populated
Free agents top-20	captured for waiver-analyst

Outputs written:

context/team-profile.md — roster snapshot updated in place (slot, player, MLB team, today's opp, status)
signals/2026-04-17-league-state.md — signal file with YAML frontmatter, source_urls, confidence

Every downstream agent (lineup-optimizer, waiver-analyst, category-strategist) now reads this signal file and team-profile.md rather than re-scraping Yahoo.

Workflow

Copy this checklist and track progress:

League State Reader Progress:
- [ ] Step 1: Read context files (league-config.md + team-profile.md)
- [ ] Step 2: Pull Yahoo pages via Claude-in-Chrome (5 URLs)
- [ ] Step 3: Parse roster, standings, matchup, FAAB, free agents
- [ ] Step 4: Update team-profile.md in place
- [ ] Step 5: Emit signal file with frontmatter + source_urls

Step 1: Read context files

Load the authoritative contract and the last known state before touching Yahoo. This both verifies the league ID/URL and provides the skeleton to diff against.

Read ~/Documents/Projects/yahoo-mlb/context/league-config.md — confirm league ID 23756, team 5, roster shape (C/1B/2B/3B/SS/3OF/2UTIL/3SP/2RP/5P/3BN/3IL = 26), FAAB budget $100
Read ~/Documents/Projects/yahoo-mlb/context/team-profile.md — capture prior FAAB remaining, prior roster for diff
Read ~/Documents/Projects/yahoo-mlb/context/frameworks/signal-framework.md — confirm signal file format
Read ~/Documents/Projects/yahoo-mlb/context/frameworks/data-sources.md — confirm the 5 Yahoo URLs

Step 2: Pull Yahoo pages via Claude-in-Chrome

The user is already authenticated in the browser. Navigate in order; parse page text; if any step fails, jump to Degraded Mode for that specific URL only (do not abort the whole run). See resources/methodology.md for the exact tool-call sequence and page-parsing patterns.

Team page: https://baseball.fantasysports.yahoo.com/b1/23756/5
Standings: https://baseball.fantasysports.yahoo.com/b1/23756?lhst=stand
Matchup: https://baseball.fantasysports.yahoo.com/b1/23756/matchup
Transactions (for FAAB): https://baseball.fantasysports.yahoo.com/b1/23756/transactions
Free agents: https://baseball.fantasysports.yahoo.com/b1/23756/players?status=A

Step 3: Parse and normalize

Extract structured data from each page. See resources/methodology.md for row-level parsing logic, and resources/methodology.md for how to reconstruct FAAB remaining from the transactions log.

Roster: for each of 26 slots, capture {slot, player, mlb_team, opp_today, status: active|IL|DTD|NA|BN}
Standings: W-L-T record, rank, per-category rank (10 cats)
Matchup: opponent name, live scoreline by category (W-L-T across the 10 cats so far this week)
FAAB: sum all -$N entries from transactions history this season; remaining = $100 - total spent
Free agents: capture top 25 by rostered% — enough for waiver-analyst to start ranking

Step 4: Update team-profile.md in place

See resources/template.md for the exact output shape. Overwrite the existing file (not append); this file is meant to always reflect "as of the latest run."

Header: ## As of YYYY-MM-DD
State table: record, rank, FAAB remaining, current opponent, acquisitions used, IL slots used
Roster snapshot: full 26-slot YAML block
Open questions: empty unless a page failed

Step 5: Emit signal file

Write ~/Documents/Projects/yahoo-mlb/signals/YYYY-MM-DD-league-state.md with YAML frontmatter per the signal framework. Every URL navigated must appear in source_urls. Degraded fetches drop confidence to 0.5; full-failure fields drop to 0.3 and are flagged. See resources/template.md.

Frontmatter: type: league-state, date, emitted_by: mlb-league-state-reader, confidence, source_urls[]
Body: roster table, standings table, matchup table, FAAB ledger, top-25 free agents
Validate via mlb-signal-emitter before writing (if that skill is available in this run); otherwise write directly

Degraded Mode

Chrome can fail for several reasons: tab not open, session expired, Yahoo rate-limiting, 500 error, unreadable DOM. Never abort the whole run. Fail gracefully per-URL.

Per-URL fallback decision tree:

Failure	Fallback
Navigation error / timeout	Retry once. If still failing, ask user: "Paste the contents of `{URL}` and I'll parse from that."
Session expired (login page returned)	Ask user: "Please log into Yahoo in your Chrome tab, then say 'retry'." Do not attempt to re-authenticate.
Page loads but parse fails (unknown layout)	Dump the first ~4000 chars of `get_page_text` into the signal file under `raw_capture:` and drop confidence to 0.4 for that field.
Free-agents page gated / empty	Mark `free_agents: []` and flag in the signal. The waiver-analyst can still run on roster + standings.
Transactions page gated	Ask user: "What's your FAAB remaining right now? Visible at the top of the transactions page." Accept user value; mark `faab_confidence: 0.6`.

User-paste template (reuse for any Yahoo page):

"I couldn't reach {URL}. Please copy the visible table on that page (select all, paste into chat) and I'll extract the fields I need from your paste."

Parse the pasted text with the same regex/row patterns as the live page. See resources/methodology.md.

Guardrails

Never assume the roster is still what it was yesterday. Waivers clear daily and trades can fire any time. Always re-read the Yahoo team page at the start of every run, even if team-profile.md looks fresh.
FAAB remaining is derived, not displayed. Yahoo's UI sometimes shows "FAAB Balance" and sometimes doesn't. The authoritative computation is: $100 minus sum of all winning bids on the transactions page this season. Do not trust a single visible number over the ledger.
Cite every URL. The signal file's source_urls: list must contain every Yahoo page actually visited. If a page was skipped because of degradation, note it in the signal body, not silently.
Do not re-scrape downstream. Once this skill has emitted today's league-state signal, lineup-optimizer / waiver-analyst / category-strategist MUST read that signal rather than re-visit Yahoo. Re-scraping wastes tokens and risks drift.
Overwrite team-profile.md; append nowhere. This file is "current state." Preserving yesterday's roster pollutes it. The append-only log lives in tracker/decisions-log.md, not here.
Status values are normalized enums. Map Yahoo's labels (P, DTD, IL-10, IL-60, NA, SUSP) to the normalized enum: active | BN | IL | DTD | NA | SUSP. Downstream agents branch on the enum, not Yahoo's strings.
Today's opponent may be blank. Off-days, postponements, and doubleheaders all produce unusual opp_today values. Record exactly what Yahoo shows (@TEX, TEX, Off, PPD, DH1/DH2) — do not normalize away information the downstream lineup-optimizer needs.
Don't emit a signal with zero source URLs. If every page failed, write an empty-body signal with confidence: 0.0 and a prominent note to the coach: "Could not reach Yahoo — paste or retry required before any downstream agent runs."

Quick Reference

The five Yahoo URLs (from context/frameworks/data-sources.md):

Team:         https://baseball.fantasysports.yahoo.com/b1/23756/5
Standings:    https://baseball.fantasysports.yahoo.com/b1/23756?lhst=stand
Matchup:      https://baseball.fantasysports.yahoo.com/b1/23756/matchup
Transactions: https://baseball.fantasysports.yahoo.com/b1/23756/transactions
Free agents:  https://baseball.fantasysports.yahoo.com/b1/23756/players?status=A

Chrome tool order (load via ToolSearch first, then call):

1. mcp__claude-in-chrome__tabs_context_mcp    (confirm active tab, auth state)
2. mcp__claude-in-chrome__navigate            (go to URL)
3. mcp__claude-in-chrome__get_page_text       (extract DOM text)
4. mcp__claude-in-chrome__read_page           (structured read if text fails)

Roster slot order (for team-profile YAML; matches league-config.md):

C, 1B, 2B, 3B, SS, OF, OF, OF, UTIL, UTIL, SP, SP, SP, RP, RP, P, P, P, P, P, BN, BN, BN, IL, IL, IL

Status enum mapping:

Yahoo	Normalized
(blank) / P	`active`
BN	`BN`
DTD	`DTD`
IL-10 / IL-60 / IL	`IL`
NA	`NA`
SUSP	`SUSP`

Signal frontmatter (minimum fields):

---
type: league-state
date: 2026-04-17
emitted_by: mlb-league-state-reader
variant_synthesis: false
confidence: 0.9
source_urls:
  - https://baseball.fantasysports.yahoo.com/b1/23756/5
  - https://baseball.fantasysports.yahoo.com/b1/23756?lhst=stand
  - https://baseball.fantasysports.yahoo.com/b1/23756/matchup
  - https://baseball.fantasysports.yahoo.com/b1/23756/transactions
  - https://baseball.fantasysports.yahoo.com/b1/23756/players?status=A
---

Key resources:

resources/template.md: team-profile.md output format, signal file output format, roster YAML schema, free-agents table schema
resources/methodology.md: Yahoo navigation sequence, parsing patterns per page, FAAB reconstruction, paste parsing, degraded-mode prompts
resources/evaluators/rubric_mlb_league_state_reader.json: 8 scoring criteria (roster completeness, FAAB accuracy, URL citation, fallback handling, etc.)

Inputs required:

Authenticated Yahoo Fantasy session in Chrome (user's responsibility)
context/league-config.md (league ID, team ID, roster shape)
context/team-profile.md (prior state, may be stub)

Outputs produced:

Updated context/team-profile.md (overwrite; reflects today's state)
signals/YYYY-MM-DD-league-state.md (with frontmatter + source_urls)
Degraded-mode prompts to user if any page fails