Prompt arguments must be strings despite needing structured data

6/10 Medium

The MCP spec requires all prompt arguments to be strings, but Python functions generating prompts often need structured data (lists, dicts) for business logic. This forces developers to manually parse JSON strings with json.loads() and handle conversion errors.

MCPPython
Category
config
Workaround
hack
Stage
build
Freshness
declining
Scope
framework
Upstream
open
Recurring
Yes
Buyer Type
team
Maintainer
active

Sources

Collection History

Query: “What are the most common pain points with FastMCP for developers in 2025?”4/8/2026

The MCP spec requires all prompt arguments to be strings. This has been a persistent developer pain point... forced developers to litter their prompt logic with `json.loads()` and pray that the agent provides a compatible input.

Created: 4/8/2026Updated: 4/8/2026