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Glama

FabTally Utility Belt

by io.github.zvmzaretsky

Live currency convert (paid $0.001)

currency

PAID $0.001. Convert an amount between currencies at reference/mid-market rates from a keyless public central-bank feed (ECB), cached. Informational, not a dealable quote. Args: amount, from, to (ISO-4217, e.g. USD, EUR, JPY). Without payment returns the x402 challenge; pass x_payment to settle.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
toYesTarget ISO-4217 code, e.g. EUR.
fromYesSource ISO-4217 code, e.g. USD.
amountYesAmount in the source currency.
x_paymentNox402 payment payload (base64) for this PAID tool. If supplied it is forwarded as the X-PAYMENT header to settle the $0.001 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?

No annotations are provided, so the description carries the full burden, and it excels: it discloses the $0.001 cost, the keyless public feed, caching, mid-market/informational nature, and the x402 challenge/payment behavior. This gives the agent a clear picture of side effects and prerequisites beyond the name and schema.

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 two dense sentences, front-loaded with the critical 'PAID $0.001' warning. Every clause adds information—source, rates, caveat, args, payment flow—with no filler or 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?

For a simple 4-param tool with no output schema or annotations, the description covers purpose, cost, data source, caching, limitation, and payment behavior. While it doesn't spell out the exact result payload, the conversion result is strongly implied, and the description provides enough for an agent to invoke and handle the payment dance correctly.

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%, giving a baseline of 3. The description adds value by listing the args, giving concrete ISO-4217 examples (USD, EUR, JPY), and explaining the x_payment parameter's role in settling the challenge. This goes beyond the schema's field descriptions.

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+resource: "Convert an amount between currencies" and adds precision with reference/mid-market rates, ECB feed, and ISO-4217 codes. This clearly distinguishes it from the sibling 'convert' tool by scoping it to live currency conversion with a specific data source.

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 clear context: it is PAID, uses cached ECB rates, is informational, and not a dealable quote. It also explains the payment flow (x402 challenge without payment, settle with x_payment). However, it does not explicitly reference the sibling 'convert' tool or state when to choose one over the other, so it falls short of a full when/when-not/exclusion set.

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

A4.1/5.0
Disambiguation5/5

Each tool targets a distinct operation: unit conversion, cron parsing, currency conversion, date math, diff, encoding, hashing, ID generation, JSON schema validation, regex, RRULE expansion, text transforms, and timezone conversion. Even related tools like convert, currency, and timezone are clearly separated by domain, with descriptions that eliminate ambiguity.

Naming Consistency5/5

All tool names are lowercase single-word identifiers without separators or camelCase, forming a clean and predictable pattern. While some are verbs (convert, diff, encode) and others nouns (cron, currency, id), the uniform naming style ensures consistency.

Tool Count5/5

13 tools is well-scoped for a general-purpose utility belt. Each tool covers a common utility without redundancy, fitting comfortably within the ideal 3-15 range.

Completeness5/5

The tool surface covers a broad range of utilities: unit and currency conversion, date/time handling (datemath, timezone, cron, rrule), text processing (text, encode, regex, diff), cryptography (hash), ID generation, and schema validation. No obvious gaps exist for the stated purpose.

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