analyze-function

A command for examining one function in a codebase, including what calls it, what it calls, its complexity, and how data moves through it.

In plain words
What is it for?
Use it to locate a function, inspect its definition, trace callers and callees, review branches and data flow, and assess complexity.
Why use it?
It helps developers understand the impact and behavior of unfamiliar code before changing it.

Command

Part of the narsil-plugin plugin — 1 skill, 5 commands shipped together

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add commands/postrv/narsil-mcp/analyze-function
Clone the repo
git clone --depth 1 https://github.com/postrv/narsil-mcp

Or install narsil-plugin, the plugin that ships this one along with the rest of its 1 skill, 5 commands.

Per session 18 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 394 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00018 $0.00394
Opus 5 $0.00009 $0.00197
Sonnet 5 $0.00004 $0.00079
Haiku 4.5 $0.00002 $0.00039

Measured 3d ago against content hash fbfed3a7a295, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

analyze-function scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

narsil-plugin/commands/analyze-function.md · 47 lines

What it actually says

Analyze Function

Perform a deep analysis of a specific function to understand its role, complexity, and impact.

Prerequisites

This command requires the --call-graph flag to be enabled when starting narsil-mcp. Check get_index_status to verify.

Workflow

The user should provide a function name. Parse $ARGUMENTS to extract:

  • Repository name (if provided)
  • Function name (required)
  1. Find the function: Use workspace_symbol_search to locate the function if the exact location is unknown

  2. Get the source: Use get_symbol_definition to read the function code

  3. Analyze callers: Use get_callers with transitive=true and max_depth=3 to see what calls this function

  4. Analyze callees: Use get_callees with transitive=true to see what this function calls

  5. Check complexity: Use get_complexity to get cyclomatic and cognitive complexity metrics

  6. Data flow (if path is known): Use get_data_flow to understand variable definitions and uses

  7. Control flow (if path is known): Use get_control_flow to see branches and loops

  8. Summarize:

    • Function purpose (based on code and naming)
    • Complexity assessment (simple/moderate/complex)
    • Dependency analysis (what it depends on, what depends on it)
    • Risk assessment for modifications
    • Suggestions for refactoring if complexity is high

Arguments

Function to analyze: $ARGUMENTS

Example usage:

  • /narsil:analyze-function handle_request
  • /narsil:analyze-function myrepo process_payment
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 47 lines · 18 tokens per session scan A fbfed3a7a295

Subscribe to this mod's changes

analyze-function is a command published in the GitHub repository postrv/narsil-mcp (181 stars, last pushed 3mo ago), licensed Apache-2.0. It adds 18 tokens to every session and 394 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.