League Loom

Get Fantasy League Info

fantasy_get_league_info

Read-onlyIdempotent

A league's name, teams (owners on ESPN/Sleeper), scoring format and settings, and key rules such as the trade deadline where the platform provides them; also the source of team ids for team_query.

Input Schema

Name	Required	Description	Default
`sport`	No	e.g. 'NFL', 'NBA'. Needed for ESPN/Sleeper and Fantrax name lookups.
`season`	No	Season year, e.g. 2025; ignored by Fantrax.
`provider`	No	Fantasy platform. Optional: defaults to your connected platform ('sleeper').
`league_id`	No	Omit when connected. League id (Fantrax also takes the league URL).
`team_query`	No	Your team's exact id (preferred) or unique name; labels it (your team). Fantrax needs it (no owner data); ESPN/Sleeper auto-detect. Ids: fantasy_get_league_info.
`credentials`	No	Only WITHOUT a connected profile: secret_id (Fantrax), espn_s2 + swid (private ESPN), username or user_id (Sleeper discovery). Public ESPN and Sleeper reads need none.
`league_query`	No	A connected league's name/id; omit to auto-pick (primary first). Never ask for ids.
`response_format`	No	'markdown' (default, most compact) or 'json' (same normalized data, not the raw payload).	markdown

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedOct 24, 2026

changedInput schema / properties / credentials / additionalProperties
```
Previous value: -trueNew value: +{}
```

changedInput schema / properties / season / anyOf

Previous value: -[
-  {
-    "type": "integer"
-  },
-  {
-    "type": "string"
-  }
-]New value: +[
+  {
+    "maximum": 9007199254740991,
+    "minimum": -9007199254740991,
+    "type": "integer"
+  },
+  {
+    "type": "string"
+  }
+]

Changed7 schema fields changedSep 29, 2026

changedInput schema / properties / credentials / description

Previous value: -"Per-call credentials, only needed WITHOUT a connected profile. Keys: secret_id (Fantrax); espn_s2 + swid (private ESPN leagues); username or user_id (Sleeper discovery); session_cookie / auth_token + write_enabled:true (explicit write opt-in only). Public ESPN leagues and all Sleeper reads need none."New value: +"Only WITHOUT a connected profile: secret_id (Fantrax), espn_s2 + swid (private ESPN), username or user_id (Sleeper discovery). Public ESPN and Sleeper reads need none."

changedInput schema / properties / league_id / description

Previous value: -"The platform's league id (Fantrax also accepts the full league URL)."New value: +"Omit when connected. League id (Fantrax also takes the league URL)."

changedInput schema / properties / league_query / description

Previous value: -"League name/id filter, for when the profile has several leagues on the provider."New value: +"A connected league's name/id; omit to auto-pick (primary first). Never ask for ids."

changedInput schema / properties / response_format / description

Previous value: -"'markdown' (default) or 'json' (raw payload)."New value: +"'markdown' (default, most compact) or 'json' (same normalized data, not the raw payload)."

changedInput schema / properties / season / description

Previous value: -"Season year, e.g. 2025. Required for ESPN/Sleeper league discovery; ignored by Fantrax."New value: +"Season year, e.g. 2025; ignored by Fantrax."

changedInput schema / properties / sport / description

Previous value: -"Sport, e.g. 'NFL', 'NBA', 'MLB', 'NHL'. Required for ESPN/Sleeper and Fantrax name lookups."New value: +"e.g. 'NFL', 'NBA'. Needed for ESPN/Sleeper and Fantrax name lookups."

changedInput schema / properties / team_query / description

Previous value: -"Your team's exact id (preferred) or a unique name fragment; marks it ⭐. Required on Fantrax (no owner data there); ESPN/Sleeper auto-detect. Team ids come from fantasy_get_league_info."New value: +"Your team's exact id (preferred) or unique name; labels it (your team). Fantrax needs it (no owner data); ESPN/Sleeper auto-detect. Ids: fantasy_get_league_info."

Changed15 schema fields changedSep 10, 2026

changedInput schema / properties / credentials / additionalProperties
```
Previous value: -falseNew value: +true
```

changedInput schema / properties / credentials / description

Previous value: -"Per-call credentials. Fill only the keys your provider needs (see fantasy_list_providers). Public ESPN leagues and all Sleeper reads need none."New value: +"Per-call credentials, only needed WITHOUT a connected profile. Keys: secret_id (Fantrax); espn_s2 + swid (private ESPN leagues); username or user_id (Sleeper discovery); session_cookie / auth_token + write_enabled:true (explicit write opt-in only). Public ESPN leagues and all Sleeper reads need none."

removedInput schema / properties / credentials / properties / espn_s2

Removed value: -{
-  "description": "ESPN private-league cookie 'espn_s2' (DevTools → Application → Cookies → espn.com).",
-  "type": "string"
-}

removedInput schema / properties / credentials / properties / secret_id

Removed value: -{
-  "description": "Fantrax Secret ID (User Profile → 'Your Secret ID').",
-  "type": "string"
-}

removedInput schema / properties / credentials / properties / swid

Removed value: -{
-  "description": "ESPN private-league cookie 'SWID': a GUID in curly braces, e.g. {XXXX-...}.",
-  "type": "string"
-}

removedInput schema / properties / credentials / properties / user_id

Removed value: -{
-  "description": "Sleeper numeric user_id (alternative to username).",
-  "type": "string"
-}

removedInput schema / properties / credentials / properties / username

Removed value: -{
-  "description": "Sleeper username (for league discovery).",
-  "type": "string"
-}

changedInput schema / properties / league_id / description

Previous value: -"The league id from the platform. For Fantrax, a full league URL is also accepted and the server extracts the id."New value: +"The platform's league id (Fantrax also accepts the full league URL)."

changedInput schema / properties / league_query / description

Previous value: -"Optional profile league name/id filter. Use when the profile has multiple leagues for the provider."New value: +"League name/id filter, for when the profile has several leagues on the provider."

changedInput schema / properties / provider / description

Previous value: -"Fantasy platform: 'fantrax', 'espn', or 'sleeper'. Call fantasy_list_providers first to see each provider's capabilities and required credentials."New value: +"Fantasy platform. Optional: defaults to your connected platform ('sleeper')."

changedInput schema / properties / response_format / description

Previous value: -"Output format: 'markdown' (default, human-readable) or 'json' (raw upstream payload)."New value: +"'markdown' (default) or 'json' (raw payload)."

changedInput schema / properties / season / description

Previous value: -"Season year, e.g. 2024. REQUIRED for espn and sleeper league discovery; ignored by fantrax."New value: +"Season year, e.g. 2025. Required for ESPN/Sleeper league discovery; ignored by Fantrax."

changedInput schema / properties / sport / description

Previous value: -"Sport, e.g. 'NFL', 'NBA', 'MLB', 'NHL'. Required for ESPN/Sleeper and for Fantrax player/name lookups."New value: +"Sport, e.g. 'NFL', 'NBA', 'MLB', 'NHL'. Required for ESPN/Sleeper and Fantrax name lookups."

changedInput schema / properties / team_query / description

Previous value: -"Identifies your team and marks it ⭐. Use the exact team id (preferred because it never breaks on rename) or a unique part of the team name. REQUIRED for Fantrax to identify your team: Fantrax exposes no owner data, so it cannot be auto-detected (ESPN/Sleeper auto-detect from your credentials). Get team ids from fantasy_get_league_info. For rosters this also filters to that team."New value: +"Your team's exact id (preferred) or a unique name fragment; marks it ⭐. Required on Fantrax (no owner data there); ESPN/Sleeper auto-detect. Team ids come from fantasy_get_league_info."

removedInput schema / required
```
Removed value: -[
-  "provider"
-]
```

First observedJun 29, 2026

TDQS

A3.6/5.0

Behavior3/5

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

Annotations already declare readOnly, idempotent, non-destructive, and openWorld, so the safety profile is covered. The description adds genuine behavioral context by qualifying that rules are returned only 'where the platform provides them,' signalling platform-dependent gaps in the payload. It says nothing about latency, multi-league resolution, or what happens when league_id is omitted, so it earns a moderate score rather than a high one.

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

Conciseness5/5

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

A single dense sentence with the returned data front-loaded and the cross-tool hint appended last. No filler, no restatement of the title, and it ends on the actionable detail.

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?

With no output schema, the description must carry the return-value burden, and it does so by listing the concrete fields returned. Given eight optional parameters and a three-provider matrix, the description is adequate because the schema documents provider behavior in detail. Minor gap: it doesn't clarify whether multiple leagues can be resolved or how the response format choice affects content, but nothing critical is missing.

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

Parameters3/5

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

Schema description coverage is 100%, so all eight parameters are already documented, including the provider defaults and credentials shape. The description only adds the cross-reference that team_query accepts ids sourced from this tool, which is a useful but narrow contribution beyond the schema. Baseline 3 applies when the schema carries the parameter burden.

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?

The description enumerates exactly what the tool returns (league name, teams/owners, scoring format and settings, rules like trade deadline) and notes it is the source of team ids. That is specific and resource-focused, though the verb is implicit ('A league's name, teams...') rather than an explicit 'Retrieve'. Sibling differentiation is only partial — it links forward to team_query but doesn't contrast with fantasy_get_my_teams or fantasy_get_standings.

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?

Usage is implied rather than stated: calling out that this is the source of team ids for team_query hints it should be called before team-scoped tools. There is no explicit 'use this when' / 'use X instead' guidance, and no mention that it is the natural entry point before standings, matchups, or rosters.

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

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