I don't see ast-grep as being very useful to an agent.

What a coding agent needs is to be able to locate portions of source code relevant to what it has been tasked with, and preferably in more context-efficient fashion than just grepping and loading entire source files into context. One way to do this is something like Cursor's vector index of code chunks, and another would be something like TreeSitter (or other identifier-based tools) that knows where identifiers (variables, functions) are defined and used.

Language servers (LSP) are not useful for this task since they can't tell the agent "where is function foo() defined" (but TreeSitter can), since as someone else noted language servers are based on location (line number) not content (symbols). Language servers are designed to help editors.

It's possible that ast-grep might be some some use to a coding agent, but looking for syntax/AST patterns rather than just identifier definitions and usages seems a much more niche facility.