MCP Connectors require tool_search on every session

MCP connectors of type mssql-* are marked as deferred tools in Claude’s system. This means that on every new session, Claude doesn’t know their parameters and calls tool_search before it can use them — even though it has used them thousands of times before.

Issue details

Field	Value
Date	2026-03-02
Severity	Low (UX / token cost)
Status	Workaround applied

Affected connectors

• mssql-MyDatabase
• mssql-MyDatabase_LOCAL
• mssql-PROD-SERVER
• mssql-SQL01
• mssql-MyIdentityDB

Impact

• Unnecessary token cost on every session that touches the database
• Extra latency — one additional call before the actual query
• All mssql-* connectors share the same function schema, making the tool_search redundant

Common function schema

All connectors expose exactly the same functions:

Function	Parameters
query_database	query: string
get_database_info	—
explore	type?: string, filter?: string, schema?: string, pattern?: string, search_in?: string
inspect	table_name: string, schema?: string, detail?: string
execute_procedure	procedure_name: string, parameters?: string

Root cause

The deferred tools system doesn’t distinguish between tools “known from training” and tools that require real discovery. All MCPs go through the same mechanism even though their schema is static and well-known.

Workaround applied

A note was added to Claude’s user memory with the complete connector schema:

mssql connectors (...): Do NOT use tool_search, call directly:
query_database(query), list_tables(), describe_table(table_name, schema?), ...

With this, Claude skips tool_search and calls the connector directly.

Ideal solution

Allow mssql-* connectors (or others with static, well-defined schemas) to be marked as pre-loaded, or have Claude recognize them by prefix without needing tool_search.