# MCP Tool Schema Token Cost Calculator

> Source: https://netray.co/tools/mcp-tool-schema-token-cost-calculator
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Estimate the tokens and monthly cost of tool definitions sent on each request, and how caching or fewer tools changes it.

## Category

developer

## Audience

- ERP developer
- AI engineer
- Solution architect

## Tool

**Kind:** calculator

**Currency:** $

**Inputs:**

#### Tools exposed to the model

**Key:** tool_count

**Type:** slider

**Default:** 24

**Min:** 1

**Max:** 100

**Step:** 1

**Unit:** tools

**Help:** All tools loaded across every connected MCP server.

#### Average tokens per tool definition

**Key:** tokens_per_tool

**Type:** number

**Default:** 250

**Min:** 20

**Step:** 10

**Unit:** tokens

**Help:** Name, description and parameter schema. Count a sample with your model's tokenizer.

#### Model requests per day

**Key:** requests_per_day

**Type:** number

**Default:** 2000

**Min:** 0

**Step:** 100

**Unit:** requests

**Help:** Every turn of a conversation counts as a request.

#### Input price per million tokens

**Key:** price_per_m

**Type:** number

**Default:** 3

**Min:** 0

**Step:** 0.5

**Unit:** $

**Help:** Use your provider's current price. For self-hosted models, use your internal cost per million.

#### Share of requests served from cache

**Key:** cached_share

**Type:** slider

**Default:** 0

**Min:** 0

**Max:** 100

**Step:** 5

**Unit:** %

**Help:** Prompt caching of the stable tool block, if your provider supports it.

#### Discount on cached input

**Key:** cache_discount

**Type:** number

**Default:** 90

**Min:** 0

**Max:** 100

**Step:** 5

**Unit:** %

**Help:** Check your provider's current cached-input pricing.

#### Model context window

**Key:** context_window

**Type:** number

**Default:** 128000

**Min:** 1000

**Step:** 1000

**Unit:** tokens

**Outputs:**

#### Tool definition tokens per request

**Key:** schema_tokens

**Expr:** tool_count * tokens_per_tool

**Format:** integer

**Primary:** true

**Description:** Sent before the user's question on every request.

#### Share of context window used

**Key:** context_share

**Expr:** schema_tokens / context_window * 100

**Format:** percent

#### Tool definition tokens per month

**Key:** monthly_tokens

**Expr:** schema_tokens * requests_per_day * 30

**Format:** integer

#### Effective billed share

**Key:** effective

**Expr:** 1 - (cached_share / 100) * (cache_discount / 100)

**Format:** decimal

**Description:** 1.0 means no caching benefit.

#### Monthly cost of tool definitions

**Key:** monthly_cost

**Expr:** monthly_tokens / 1000000 * price_per_m * effective

**Format:** currency

**Primary:** true

#### Monthly cost per tool

**Key:** cost_per_tool

**Expr:** monthly_cost / tool_count

**Format:** currency

**Chart:**

#### Tool definition tokens vs tools exposed

**Type:** line

**X:** tool_count

**From:** 1

**To:** 100

**Steps:** 25

**Series:**

- schema_tokens

**Disclaimer:** An estimate. Real token counts depend on the model tokenizer and schema detail, and provider pricing and caching rules change. Treat results as a planning range.

## Content

**Intro:** Every tool an MCP client loads is described to the model on every request. Add a few servers and the tool block can reach tens of thousands of tokens before the user has typed a word. This calculator shows what that costs in context and money.

**Sections:**

#### How to use the calculator

**Body:** Set the number of tools across all connected servers, not just one. Estimate the average tokens per definition by pasting two or three real tool definitions into your model's tokenizer and averaging. Enter daily requests, counting each turn of a conversation, then your input price. If your provider caches stable prompt prefixes, set the cached share and discount. The results show tokens per request, share of the context window, monthly volume and monthly cost.

#### The formula

**Body:** Tool definition tokens equal tool count times average tokens per tool. Monthly tokens equal that figure times daily requests times thirty. Cost equals monthly tokens divided by one million, times the input price, times the effective billed share. The effective share is one minus cached share times cache discount, so a 90 percent discount on 80 percent of requests bills about 28 percent of the full amount. The chart sweeps tool count to show the linear growth.

#### Reading the result

**Body:** With 24 tools at 250 tokens, the block is 6,000 tokens per request, under 5 percent of a 128,000 token window. Fine on its own, but the cost compounds with traffic, and the harder penalty is accuracy: models choose less reliably when many similar tools compete. If the share passes 10 to 15 percent, consider splitting servers by domain, loading tools on demand or shortening descriptions.

**Bullets:**

- Split servers by domain so each agent sees fewer tools
- Shorten descriptions but keep enums and units explicit
- Use caching for the stable tool block where supported
- Remove tools nobody has called in a month

#### Common mistakes

**Body:** People count only their own server and forget the others loaded by the client. They also estimate tokens from character counts, which varies a lot for JSON schemas, and forget that multi-turn agents resend the block on every turn. Finally, optimizing for cost alone can strip the descriptions that make tool selection accurate, so re-run your evaluation set after any trimming.

**Cta:** Netray designs agent tool layers over ERP to be small and well described. If your tool block is bloating prompts, we can help restructure it.

**Faq:**

#### How many tokens does a typical MCP tool use?

**Answer:** It varies widely. A simple tool with two parameters may be under 100 tokens, while one with many parameters and long descriptions can exceed 500. Measure a few of yours with your model's tokenizer.

#### Does prompt caching apply to tool definitions?

**Answer:** Many providers can cache a stable prompt prefix, which often includes tool definitions. Rules, minimum sizes and discounts differ and change, so check your provider's current documentation.

#### Is there a limit on how many tools I should expose?

**Answer:** No universal limit, but accuracy tends to fall as similar tools multiply. Keep each agent's toolset focused and split large catalogs by domain.

#### Does this apply to self-hosted models?

**Answer:** Yes for context and latency. Use your internal cost per million tokens in the price field, or set it to a GPU-hour based estimate.

## Search terms

mcp tool definitions token cost, mcp context window usage, tool schema token calculator, too many mcp tools, llm tool definition cost, prompt caching savings calculator, mcp server token overhead

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