GridIron Data

Find a player by NFL GSIS id

get_player_by_gsis_id

Read-onlyIdempotent

Returns the player with this NFL GSIS id (e.g. "00-0034857", the key nflverse and NFL data use), as the same record get_player returns, with an ids map (gsis, pfr, pff, nfl, espn, sleeper) from the daily nflverse crosswalk. Use it to join nflverse or NFL data to GridIron. Free plan.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "gsis_id": "<gsis_id>"
    },
    "name": "get_player_by_gsis_id"
  }
}

Input Schema

Name	Required	Description	Default
`gsis_id`	Yes	NFL GSIS id, the key nflverse and NFL data use.

Output Schema

Name	Required	Description
`ids`	No	Other systems' ids (gsis, pfr, pff, nfl, espn, sleeper) from the nflverse crosswalk.
`note`	No	A sentence for the user saying which plan is needed.
`team`	No	Current team code.
`error`	No	Present only when the call failed: what went wrong.
`reason`	No	Machine-readable failure reason, e.g. basic_required or pro_required.
`status`	No	HTTP status of the failed API call.
`position`	No	Position.
`player_id`	No	GridIron player id ("First Last#POS").
`player_name`	No	Player name.
`upgrade_url`	No	Where to see the plans.
`required_plan`	No	The plan that unlocks this data: basic or pro.
`espn_player_id`	No	ESPN athlete id.

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 10, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds real value beyond that: the record is identical to get_player's output, it carries an ids crosswalk (gsis, pfr, pff, nfl, espn, sleeper), the crosswalk is refreshed daily, and it is a free-plan call.

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

Conciseness4/5

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

One front-loaded sentence that states the return value first and the use case last, with no filler. It is dense with stacked parentheticals, which slightly slows parsing but every clause carries information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a single-parameter read with an output schema and full annotations, nothing needed for correct invocation is missing: key format, return shape, provenance, freshness and the join scenario are all stated. The output schema relieves the description of enumerating return fields.

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 coverage is 100% and the single parameter already documents its meaning, pattern and an example. The description's parenthetical repeats the same example and framing rather than adding new syntax or edge-case meaning, so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

Names a specific verb and resource ("Returns the player") plus the exact lookup key (NFL GSIS id) and anchors it to a known record shape ("the same record get_player returns"). An agent can distinguish this from get_player_by_espn_id purely by which key it holds, without opening either schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives a concrete when-to-use rule: "Use it to join nflverse or NFL data to GridIron," which tells the agent the precondition (holding an nflverse/NFL key). It stops short of naming a sibling to use instead when the caller has an ESPN id or a name, which would have made it a 5.

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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