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AI APIs Differ in Tool List Acceptance Rules, Study Finds

By PulseAugur Editorial · [1 sources] ·

A recent analysis examined the tool lists submitted to three AI APIs: Claude Haiku 5.5, GPT-5 nano, and Gemini 2.5-Flash. The study found that each API enforces its own unique rules for accepting tool lists, leading to varying refusal rates. Anthropic's API refused 456 lists, OpenAI's refused 591, and Google's refused 7, with an additional 135 unexplained refusals. The findings suggest that server authors should adhere to specific naming conventions, uniqueness, schema types, and tool count limits to ensure broader API compatibility. AI

IMPACT Developers need to be aware of differing API rules for tool lists to ensure broader compatibility and avoid refusals.

RANK_REASON The item details a study and its findings regarding the behavior of AI APIs. [lever_c_demoted from research: ic=1 ai=1.0]

Read on dev.to — MCP tag →

AI-generated summary · Google Gemini · from 1 sources. How we write summaries →

AI APIs Differ in Tool List Acceptance Rules, Study Finds

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11 / 100
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Tool
The item details a study and its findings regarding the behavior of AI APIs. [lever_c_demoted from research: ic=1 ai=1.0]
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product, infra
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High
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Breaking (< 6h)
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COVERAGE [1]

  1. dev.to — MCP tag TIER_1 English(EN) · md sultan mahamud ·

    "Your MCP server's tool list can be refused before the model sees it: the rules three AI APIs applied to 21,812 lists"

    <p>We read the tool lists of MCP servers in the official MCP registry. Then we sent each list, once, to three small AI models through their vendors' Batch APIs: Claude Haiku 5.5, GPT-5-nano and Gemini 2.5 Flash. Each model was set to its lowest reasoning level and got one fixed r…

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