BetterChess

Analyse a chess position

chess_analyse

Read-only

Returns an engine evaluation of a chess position: the strongest candidate moves with their scores, and the position's checkable facts — side to move, whether that side is in check, undefended pieces and the pieces attacking them, and the material balance. Accepts a FEN, a PGN, or a list of SAN moves from the starting position. Also reports what the OPPONENT would play if it were their turn, which is the difference between a position being quiet and merely looking quiet. Pass considering with a move you are thinking of playing and it returns what that move actually walks into — a losing move is usually not in the top candidates, so asking about it directly is the only way to find out.

Input Schema

TableJSON Schema

Name	Required	Description
`fen`	No	FEN of the position.
`pgn`	No	PGN; the position after the final move is used.
`moves`	No	SAN moves from the start, e.g. ["e4","e5"].
`traps`	No	Also scan the captures and checks available to the side to move and return the ones that lose, each with its refutation. Slower — several extra searches.
`multipv`	No	How many candidate moves (1-5, default 3).
`considering`	No	A move you are thinking of playing, in SAN, e.g. "Ng5". Returns the evaluation after it and the line that refutes it.

Schema Changelog

Changes observed during successful MCP inspections. Dates show when Glama detected each change.

Changed1 schema field changedSep 2, 2026

addedInput schema / properties / traps

Added value: +{
+  "description": "Also scan the captures and checks available to the side to move and return the ones that lose, each with its refutation. Slower — several extra searches.",
+  "type": "boolean"
+}

Changed1 schema field changedSep 2, 2026

addedInput schema / properties / considering

Added value: +{
+  "description": "A move you are thinking of playing, in SAN, e.g. \"Ng5\". Returns the evaluation after it and the line that refutes it.",
+  "type": "string"
+}

First observedSep 1, 2026

TDQS

A4.4/5.0

Behavior5/5

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

Annotations already declare readOnlyHint=true, so the read-only nature is known. The description goes further by disclosing nuanced behavior: it returns what the opponent would play, explains that a losing move may not appear among top candidates (making direct inquiry necessary), and warns that the traps option is slower due to extra searches. No contradictions with annotations.

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?

The description is longer than average but each sentence earns its place: it lists outputs, accepted inputs, the opponent-response feature, and the considering-mode use case. Structure is logical with a flow from general function to specific parameter guidance. Slight redundancy in explaining the considering mode twice, but overall efficient for the tool's complexity.

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 tool with 6 optional parameters and no output schema, the description sufficiently explains inputs, behavior, and expected return contents. It covers all parameter use cases, explains edge-case behavior (losing moves not top-ranked), and clarifies the traps option's performance cost. An agent can confidently select and invoke this tool based on the description alone.

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 the baseline is 3. The description adds context for the 'considering' parameter ('what that move actually walks into') and the 'traps' behavior, but this largely reiterates schema descriptions. It does not add new parameter semantics beyond what the schema already provides; it stays at baseline.

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?

The description opens with a specific verb ('Returns an engine evaluation') and resource ('a chess position'), then enumerates concrete outputs: candidate moves with scores, checkable facts, opponent response, and a considering-mode. This clearly distinguishes it from sibling tools like chess_review or chess_attacks by focusing on quantitative engine analysis rather than review or attack visualization.

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?

The description explicitly explains when to use the 'considering' parameter (to test a move you're thinking of) and mentions the value of checking opponent responses. It implies the general use case of analyzing a position, but does not explicitly contrast with sibling tools or state when not to use this tool. The guidance is clear but incomplete regarding alternatives.

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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TDQS

A4.2/5.0

Disambiguation5/5

Each tool has a clearly distinct purpose: analyse evaluates positions, attacks lists attacked squares, review replays games for blunders, and rig generates coaching script. No ambiguity between them.

Naming Consistency4/5

All tools share the 'chess_' prefix, and the suffixes are short and meaningful. There is a slight mix of verb-like and noun-like suffixes (analyse, attacks, review, rig), but the pattern is still predictable and readable.

Tool Count4/5

Four tools is appropriate for a chess analysis server, covering analysis, tactics, game review, and a special integration rig. Not too many, not too few, though it might feel slightly minimal for broader chess workflows.

Completeness4/5

The core analysis functions are present: position evaluation, attack squares, game review, and a browser rig. Missing features like move legality checks or board state retrieval are minor gaps that don't block primary use cases.

Resources

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