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# Claude 5.5 or GPT-6: Which Tier Should Run Your Bot's Connected Tool?

Anthropic's Claude 5.5 family and OpenAI's GPT-6 family both now ship three price tiers, and each has its own rules for billing tool calls. This piece lines up the current rates and tool-call requirements, runs one illustrative monthly cost example for a bot that calls a connected tool thousands of times, and gives a concrete rule for when to move up a tier.

By BotBento Editorial · Published 2026-11-01 · Updated 2026-11-01

AI-assisted editorial: researched and drafted with AI using the primary sources linked below. Check the cited evidence and any stated test scope. Illustrative examples are not measured product results. [Editorial policy](/editorial/).

## In this article

- [The question a model-comparison post usually skips](#the-decision)
- [Claude's 5.5 lineup: three tiers, two tool-billing rules](#claude-tool-call-costs)
- [OpenAI's GPT-6 lineup: three tiers, an API requirement](#openai-tool-call-costs)
- [Illustrative example: a 4,400-call-a-month lookup bot](#worked-example)
- [The decision: start cheap, move up only with evidence](#decision-rule)[Read as Markdown ](/text/blog/claude-5-5-vs-gpt-6-tool-calling-bot-model-choice/index.md)

## Key takeaways

- Claude Opus 5.5 ($4/$20 per million tokens), Sonnet 5.5 ($2/$10), and Haiku 5.5 ($0.10/$0.50 under 100K tokens) line up almost exactly with GPT-6 Astra ($10/$50), GPT-6.1 Sol ($2/$10), and GPT-6 Luna ($0.10/$0.50) — pick by task difficulty, not brand.
- Your own connected tool's definition and results are billed as ordinary input tokens on both platforms; the per-call fees only apply to each provider's hosted tools like web search ($10/1,000 calls on both) and file search.
- GPT-6 Astra and GPT-6.1 Sol require the Responses API for tool calling — a Chat Completions integration built for GPT-6 Sol or Luna with function calling won't carry over without code changes.

## The question a model-comparison post usually skips

Most "which model should I use" posts compare benchmark scores. For a small-team bot that calls one connected tool over and over — a calendar lookup, an order-status check, a ticket classifier — the more useful question is cost per call at your real volume, plus whether the tier you pick forces an API migration. Anthropic and OpenAI both currently sell three price tiers that map onto the same three jobs: cheap high-volume classification, a mid-tier workhorse, and an expensive tier for work that genuinely needs it. The decision is which tier your tool-calling task actually needs, checked against what each provider charges for the tool call itself, not just the base model.

## Claude's 5.5 lineup: three tiers, two tool-billing rules

Anthropic's current lineup is Claude Opus 5.5, Sonnet 5.5, and Haiku 5.5. Opus 5.5 is built for long-running agentic coding and knowledge work, priced at $4 / $20 USD per million input / output tokens. Sonnet 5.5 is priced the same as Sonnet 5 at $2 per million input tokens and $10 per million output tokens, but it typically needs far fewer tokens to do the same work. Haiku 5.5 costs $0.10 per million input tokens and $0.50 per million output tokens for prompts up to 100K tokens, and $0.50 per million input tokens and $2.50 per million output tokens for prompts over 100K tokens.

For a bot that calls your own connected tool (a function you define), the tool's definition and its result are priced the same as any other Claude API request, although server-side tools can incur additional charges based on their specific usage, and the API automatically includes a special system prompt for the model that enables tool use. That system-prompt overhead is small and token-based, not a per-call fee. Anthropic's own hosted tools are billed separately: web search is available on the Claude API for $10 USD per 1,000 searches, plus standard token costs for search-generated content, while code execution carries no additional charges beyond standard token costs when it runs alongside web search or web fetch. None of the three current Claude models bills by prompt length except Haiku 5.5, which is priced by prompt length and moves to the higher row once a request's total input tokens — including cache reads and writes — cross 100,000.

Sources: [Claude Opus 5.5 - Claude Platform Docs](https://platform.claude.com/docs/en/models/opus-5-5/overview), [Claude Sonnet 5.5](https://www.anthropic.com/claude/sonnet), [Claude Haiku 4.5](https://www.anthropic.com/claude/haiku), [Pricing - Claude Platform Docs](https://platform.claude.com/docs/en/about-claude/pricing), [Web search tool - Claude Platform Docs](https://platform.claude.com/docs/en/agents-and-tools/tool-use/web-search-tool), [Code execution tool - Claude Platform Docs](https://platform.claude.com/docs/en/agents-and-tools/tool-use/code-execution-tool).

## OpenAI's GPT-6 lineup: three tiers, an API requirement

OpenAI's current flagship lineup is GPT-6 Astra, GPT-6.1 Sol, and GPT-6 Luna, priced per million tokens (short context) at $10.00 input / $50.00 output for Astra, $2.00 / $10.00 for Sol, and $0.10 / $0.50 for Luna, with cached input at $1.00, $0.10, and $0.01 respectively. GPT-6 Astra is positioned as OpenAI's most capable model for complex reasoning, coding, computer use, research, and document creation, while GPT-6.1 Sol is pitched as near-Astra performance at a lower cost and Luna is the volume tier.

The tool-calling detail that catches integrations off guard: GPT-6 Astra, GPT-6.1 Sol, and GPT-6.1 Terra support Chat Completions, but tool calling requires Responses, while GPT-6 Sol and GPT-6 Luna support function calling in Chat Completions only with reasoning\_effort set to none. So a bot built against the older Chat Completions pattern needs a Responses API migration to use Astra or Sol for tool calls at all. Function definitions themselves count against the model's context limit and are billed as input tokens on every request, whether or not the model actually calls them, which matters if your bot carries a large tool library. For OpenAI's hosted tools, the published rates are $10.00 per 1,000 calls for web search (plus search content tokens billed at model rates) and $2.50 per 1,000 calls for file search, separate from whatever model tokens the call consumes.

Sources: [Pricing | OpenAI API](https://developers.openai.com/api/docs/pricing), [GPT-6 Astra Model | OpenAI API](https://developers.openai.com/api/docs/models/gpt-6-astra), [Using GPT-6 | OpenAI API](https://developers.openai.com/api/docs/guides/latest-model), [Function calling | OpenAI API](https://developers.openai.com/api/docs/guides/function-calling).

## Illustrative example: a 4,400-call-a-month lookup bot

This is a hypothetical scenario to show the arithmetic, not a measured benchmark. Say a small-team support bot calls a single connected tool (an order-status lookup) 200 times a day across 22 working days — 4,400 calls a month — and each call carries roughly 1,200 input tokens (conversation, tool definition, and tool result combined) and 250 output tokens. That's about 5.28 million input tokens and 1.1 million output tokens a month.

On the cheap tier, Claude Haiku 5.5 or GPT-6 Luna, that works out to roughly $0.53 + $0.55 ≈ $1.08 a month in base token cost. On the mid tier, Claude Sonnet 5.5 or GPT-6.1 Sol, the same traffic costs roughly $10.56 + $11.00 ≈ $21.56 a month. On the top tier, Claude Opus 5.5 or GPT-6 Astra, it's roughly $21.12 + $22.00 ≈ $43.12 on Opus 5.5, or $52.80 + $55.00 ≈ $107.80 on Astra, since Astra's output rate is 5x Sol's rather than 2x. These numbers exclude caching, retries, effort-level overhead, and any hosted search tool fee — if the bot used OpenAI's or Anthropic's hosted web search instead of its own function, the 4,400 calls would add about $44 a month in per-search fees alone, on top of the token cost for whatever content comes back.

Sources: [Claude Opus 5.5 - Claude Platform Docs](https://platform.claude.com/docs/en/models/opus-5-5/overview), [Claude Sonnet 5.5](https://www.anthropic.com/claude/sonnet), [Claude Haiku 4.5](https://www.anthropic.com/claude/haiku), [Pricing | OpenAI API](https://developers.openai.com/api/docs/pricing).

## The decision: start cheap, move up only with evidence

For a routine, well-defined tool call — status lookups, classification, extraction, routing — start on Haiku 5.5 or Luna. The cost difference to the mid tier is roughly 20x on this illustrative traffic, and that gap only grows with call volume. Move to Sonnet 5.5 or GPT-6.1 Sol when the cheap tier's error rate on your own test cases is too high to live with; both sit at the same $2/$10 rate, so the practical choice there often comes down to which API you're already using and whether you need the Responses API's tool-calling requirements anyway. Reserve Opus 5.5 or Astra for tasks where a wrong tool call is expensive to undo — multi-step writes, financial actions, anything a human would want double-checked — since Astra's output rate alone is five times Sol's and Opus 5.5 is double Sonnet 5.5.

Two caveats worth checking before you commit a budget. First, long prompts change the math differently on each platform: Claude 4.6 and later models, except Haiku 5.5, bill a 900,000-token request at the same per-token rate as a 9,000-token one, while GPT-6 Astra and GPT-6.1 Sol double their input and cache rates and raise output 1.5x once a request passes 272,000 input tokens. Second, none of the figures above is a measured head-to-head result — they're token-rate arithmetic on a hypothetical traffic pattern. Before locking in a tier, run your own evaluation on representative calls from your bot and compare completions and retries, not just the per-token sticker price.

Sources: [Pricing - Claude Platform Docs](https://platform.claude.com/docs/en/about-claude/pricing), [GPT-6 Astra Model | OpenAI API](https://developers.openai.com/api/docs/models/gpt-6-astra).

## Primary sources

Sources checked 2026-11-01. Standards and product documentation can change; follow the linked version when implementing.

- [Claude Opus 5.5 - Claude Platform Docs](https://platform.claude.com/docs/en/models/opus-5-5/overview) — Anthropic
- [Claude Sonnet 5.5](https://www.anthropic.com/claude/sonnet) — Anthropic
- [Claude Haiku 4.5](https://www.anthropic.com/claude/haiku) — Anthropic
- [Pricing - Claude Platform Docs](https://platform.claude.com/docs/en/about-claude/pricing) — Anthropic
- [Web search tool - Claude Platform Docs](https://platform.claude.com/docs/en/agents-and-tools/tool-use/web-search-tool) — Anthropic
- [Code execution tool - Claude Platform Docs](https://platform.claude.com/docs/en/agents-and-tools/tool-use/code-execution-tool) — Anthropic
- [Pricing | OpenAI API](https://developers.openai.com/api/docs/pricing) — OpenAI
- [GPT-6 Astra Model | OpenAI API](https://developers.openai.com/api/docs/models/gpt-6-astra) — OpenAI
- [Using GPT-6 | OpenAI API](https://developers.openai.com/api/docs/guides/latest-model) — OpenAI
- [Function calling | OpenAI API](https://developers.openai.com/api/docs/guides/function-calling) — OpenAI

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