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Explain effect row

explain_effect_row
Read-onlyIdempotent

Explains a function's effect row with per-effect explanations, revealing what the function may do. Use it to interpret unfamiliar effects or inspect a named function's type and effects.

Instructions

Explain a function's effect row: the canonical row plus a one-sentence explanation of each effect. Use it for 'what may this function do' or to interpret an unfamiliar effect. It covers one named function; use infer_type for an arbitrary expression's row and emit_actor_effect_graph for what an actor transitively does. Returns type, effect_row, open (the row ends in a row variable, so it may carry more effects than listed), pure (closed and empty), and effects, each with effect and explanation. A name of non-function type is not_a_function; an unknown name is not_found with the available names in error.data.available. Read-only: compiles the file's directory in memory (cached until a sibling changes) and writes or executes nothing. Failures are isError results with a stable error.code: file_not_found, read_error, invalid_params, parse_error, or check_error, the last two carrying coded diagnostics in error.data.diagnostics.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
fileYesPath to a .hird source file, absolute or relative to the server's working directory. Every .hird file in its directory is compiled with it as one program, so imported names resolve; answers may name a sibling file.
fn_nameYesThe function's name, as the file's source would write it: a local definition, a member imported with `use Mod.{name}`, or `Qualifier.name` through `use Mod`.

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
fileYes
nameYes
openYes
pureYes
typeYes
effectsYes
effect_rowYes

Schema Changelog

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

  1. Changed2 schema fields changed
    • changedInput schema / properties / file / description
      Previous value: -"Path to a .hird source file. Its directory's .hird files are compiled together as one program, so imported names resolve."New value: +"Path to a .hird source file, absolute or relative to the server's working directory. Every .hird file in its directory is compiled with it as one program, so imported names resolve; answers may name a sibling file."
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
      +  "properties": {
      +    "effect_row": {
      +      "type": "string"
      +    },
      +    "effects": {
      +      "items": {
      +        "properties": {
      +          "effect": {
      +            "type": "string"
      +          },
      +          "explanation": {
      +            "type": "string"
      +          }
      +        },
      +        "required": [
      +          "effect",
      +          "explanation"
      +        ],
      +        "type": "object"
      +      },
      +      "type": "array"
      +    },
      +    "file": {
      +      "type": "string"
      +    },
      +    "name": {
      +      "type": "string"
      +    },
      +    "open": {
      +      "type": "boolean"
      +    },
      +    "pure": {
      +      "type": "boolean"
      +    },
      +    "type": {
      +      "type": "string"
      +    }
      +  },
      +  "required": [
      +    "effect_row",
      +    "effects",
      +    "file",
      +    "name",
      +    "open",
      +    "pure",
      +    "type"
      +  ],
      +  "type": "object"
      +}
  2. Changed2 schema fields changedv0.1.1
    • changedInput schema / properties / file / description
      Previous value: -"Path to a .hird source file."New value: +"Path to a .hird source file. Its directory's .hird files are compiled together as one program, so imported names resolve."
    • changedInput schema / properties / fn_name / description
      Previous value: -"The function's name."New value: +"The function's name, as the file's source would write it: a local definition, a member imported with `use Mod.{name}`, or `Qualifier.name` through `use Mod`."
  3. First observedv0.1.0

TDQS

A4.8/5.0
Behavior5/5

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

Annotations already cover readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds value beyond those: it discloses in-memory directory compilation with caching until a sibling changes, states it writes/executes nothing, explains the open/pure return semantics, and enumerates stable error codes with the diagnostic payload location. No contradiction with annotations; substantial additive context.

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 dense (~150 words) but every sentence carries distinct information: purpose, usage, return shape, error handling, read-only behavior, and error codes. It is front-loaded with purpose and usage before details. Slightly long but justified given the tool's error-handling and return complexity; no filler.

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?

Despite an output schema being present, the description still explains the semantic meaning of return fields (open, pure, effects with explanations) and error contract. It covers purpose, when-to-use, alternatives, behavior, and failure modes exhaustively. Nothing an agent needs to call it correctly is missing.

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

Parameters4/5

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

Schema coverage is 100% and both parameters (file path, fn_name) are well documented in the schema, so baseline is 3. The description adds error-handling semantics for fn_name beyond the schema: a non-function name yields not_a_function, an unknown name yields not_found with available names in error.data.available. This enriches parameter behavior meaningfully, earning a 4.

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 states a specific verb and resource: 'Explain a function's effect row: the canonical row plus a one-sentence explanation of each effect.' It distinguishes itself from siblings by explicitly naming infer_type (arbitrary expression's row) and emit_actor_effect_graph (transitive actor effects), so an agent can tell them apart without opening schemas.

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

Usage Guidelines5/5

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

The description gives explicit when-to-use guidance: 'Use it for "what may this function do" or to interpret an unfamiliar effect.' It also states what it covers ('one named function') and names the alternatives with their selection criteria (infer_type for arbitrary expressions, emit_actor_effect_graph for transitive actor effects), leaving nothing to inference.

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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