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Signature Help

signatureHelp

Read-only

Retrieve signature information for a function or method at a call site, showing parameter names, types, and documentation for each overload. Use when cursor is inside parentheses to see expected arguments.

Instructions

Get function/method signature information at a call site. Returns parameter names, types, and documentation for each overload. Use when the cursor is inside function call parentheses to understand what arguments are expected.

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": {
      "file": "<file>",
      "line": "<line>",
      "offset": "<offset>"
    },
    "name": "signatureHelp"
  }
}

Input Schema

Name	Required	Description
`file`	Yes	File path (absolute or relative to cwd)
`line`	Yes	1-based line number
`offset`	Yes	1-based column offset (inside the parentheses)
`triggerReason`	No	Optional reason for triggering signature help

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.1.1Jul 12, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already indicate readOnlyHint=true. The description adds that it returns parameter names, types, and documentation, which informs the agent about the nature of the response without contradicting annotations.

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?

Two sentences with no fluff. The description is front-loaded, concise, and every sentence adds value.

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?

The description sufficiently explains the return value (parameter names, types, documentation) even without an output schema. Missing edge cases or error conditions, but adequate for a well-defined tool.

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%, so baseline is 3. The description adds context about when to use (inside parentheses) but does not explain individual parameters beyond what the schema already provides.

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 explicitly states it retrieves function/method signature information at a call site, including parameter names, types, and documentation for each overload. This clearly distinguishes it from sibling tools like quickinfo or definition.

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 provides explicit when-to-use guidance: 'Use when the cursor is inside function call parentheses to understand what arguments are expected.' It does not mention when not to use, but the context is clear.

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