Skip to main content
Glama

FabTally Decode

by io.github.zvmzaretsky

Resolve a selector or event topic to a signature (paid $0.001)

selector_lookup

PAID $0.001 (x402, USDC on Base). Resolve a 4-byte function selector (0x + 8 hex) OR a 32-byte event topic hash (0x + 64 hex) to its human-readable signature(s) via 4byte.directory + openchain.xyz. Returns all matches (selectors can collide) with a verified flag. Without payment returns the x402 challenge; pass x_payment to settle.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
selectorYesA 4-byte function selector (0x + 8 hex) or a 32-byte event topic hash (0x + 64 hex).
x_paymentNox402 payment payload (base64) for this PAID decode. If supplied it is forwarded as the X-PAYMENT header to settle the call and return the real result instead of a 402 challenge. Omit to get the price challenge first.

Schema Changelog

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

  1. First observed

TDQS

A4.7/5.0
Behavior5/5

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

With no annotations, the description carries full burden and does an excellent job. It discloses the paid nature ($0.001, x402, USDC on Base), the use of external APIs (4byte.directory + openchain.xyz), the possibility of collisions, the verified flag, and the 402 challenge/settle behavior.

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?

The description is a compact paragraph with every sentence contributing essential information. It front-loads the critical 'PAID' warning, then states the core function, return characteristics, and payment flow without redundancy.

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?

Given there is no output schema and no annotations, the description provides sufficient context: input format, output highlights (all matches, verified flag), payment mechanics, and the challenge/settle flow. This is adequate for an agent to use the tool correctly without additional documentation.

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%, so parameters are already documented. The description adds meaningful context for x_payment (forwarded as X-PAYMENT header, omitted to obtain challenge) and clarifies the selector format. It doesn't add much beyond the schema for selector but the payment parameter behavior is valuable.

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 action: resolve a 4-byte function selector or 32-byte event topic hash to human-readable signature(s). It clearly distinguishes from sibling tools like decode_calldata and decode_log by focusing on signature resolution rather than data decoding, and mentions the external directories used.

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?

Clear context is provided: when to use (given a selector/topic, to get signatures), and the payment flow is explicitly described (without payment you get a challenge, pass x_payment to settle). However, it does not explicitly mention when not to use or compare against the sibling tools, so it stops short of a 5.

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

All FabTally Decode toolsInspect
Try in Browser
RayrunBuild, deploy, and operate MCP servers without becoming an infrastructure team.ray.runAd

Glama MCP Gateway

Add one secure layer between your agents and this server.

TDQS

A4.5/5.0
Disambiguation5/5

Each tool has a clearly distinct purpose: fetching ABIs, decoding function calldata, decoding event logs, and resolving selectors/topics. There is no overlap in what they do, and their scopes are mutually exclusive.

Naming Consistency4/5

All names are lowercase snake_case and concise, but they mix verb-first (decode_calldata, decode_log) with noun-first (abi_fetch, selector_lookup) patterns. This is a minor deviation from a uniform verb_noun convention, but still predictable and readable.

Tool Count5/5

Four tools is a well-scoped size for a specialized decoding server. Each tool covers a necessary step in the decoding workflow without redundancy or bloat.

Completeness5/5

The tool set covers ABI retrieval, calldata decoding, event log decoding, and signature lookup, providing a complete lifecycle for decoding EVM data with no obvious dead ends. Optional ABI inputs allow flexible fallback to public sources.

Resources