Hopi

Market cap calculator

hopi_market_cap_calculator

Read-onlyIdempotent

Calculate a coin's market cap (price times circulating supply) and fully diluted valuation, or work backwards to the price implied by a target market cap. Works in any currency; nothing is looked up. Source: https://hopi.co.uk/market-cap-calculator/

Input Schema

TableJSON Schema

Name	Required	Description
`mode`	Yes	market_cap: price times supply. implied_price: target cap divided by supply.
`price`	No	Current price per coin (for market_cap)
`supply`	Yes	Circulating supply (for both modes)
`target`	No	Target market cap (for implied_price)
`current`	No	Current price per coin, to show the multiple (optional, implied_price mode)
`maxSupply`	No	Maximum or total supply for FDV (optional, market_cap mode)

Output Schema

TableJSON Schema

Name	Required	Description
`mode`	Yes
`approx`	No
`summary`	Yes
`marketCap`	No
`source_url`	Yes	The tool's page on hopi.co.uk (cite or open to check the figure)
`marketCapString`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 20, 2026
- addedOutput schema / required
```
Added value: +[
+  "mode",
+  "source_url",
+  "summary"
+]
```
First observedSep 20, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Beyond the readOnlyHint and idempotentHint annotations, the description adds valuable behavioral context: 'nothing is looked up' and 'works in any currency'. This clarifies that no external data is fetched and currency units are irrelevant, which annotations do not convey.

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 dense sentences deliver the purpose, modes, formulas, currency flexibility, and no-lookup behavior, with a source link at the end. Every element earns its place and the key formulas are front-loaded.

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 the 100% schema coverage, the annotations, and the presence of an output schema, the description is complete for a simple calculator. It covers both modes, explains the formulas, and sets expectations about not performing live lookups.

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?

The schema already fully documents all six parameters, giving a baseline of 3. The description adds formula-level meaning—market cap as price times supply, implied price as target cap divided by supply, and FDV via maxSupply—which goes beyond the schema's individual property 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?

Description states a specific verb ('Calculate') and resource ('a coin's market cap'), includes the core formula, and explains the two supported modes: forward calculation and working backwards to implied price. This clearly distinguishes it from sibling calculators like crypto profit or position size.

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 makes the usage context clear: it is a pure calculation tool that works in any currency and performs no lookups. It doesn't explicitly mention alternatives or exclusions, but the context is sufficient for an agent to know when this tool fits.

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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