feat: add date-based filtering to discord_read_messages

[hugo-clemente]

Summary

Adds before, after, and around parameters to discord_read_messages. All three accept a Discord snowflake ID or an ISO 8601 date string (e.g. 2025-03-01T00:00:00Z). Date strings are converted to synthetic snowflakes using Discord's epoch offset.

Only one of the three can be specified per call. A Zod refinement enforces this at parse time.

Motivation

discord_read_messages currently only fetches the N most recent messages. There's no way to request messages from a specific time range, which makes it hard to look up older conversations or paginate through channel history. Discord's API already supports before/after/around as snowflake-based cursors, so this just wires that up and also accepts ISO dates.

Testing

Tested locally against a live Discord server.

Test	Result
after with ISO date	Only messages after that date returned
before with ISO date	Only messages before that date returned
around with ISO date	Messages centered around the date
Raw snowflake ID passed to before	Passed through unchanged
Both before and after specified	Validation error
Invalid string	Descriptive error thrown
No filtering params (existing behavior)	Unchanged
npm run build	Clean

Changes

5 files changed, same schema/handler/toolList pattern as the rest of the codebase:

File	Change
src/utils/snowflake.ts	New — dateToSnowflake, isSnowflake, resolveSnowflakeOrDate
src/schemas.ts	Added before/after/around to ReadMessagesSchema with mutual exclusion refinement
src/tools/channel.ts	Builds fetch options from new params, passes to channel.messages.fetch()
src/toolList.ts	Updated description and inputSchema for discord_read_messages
README.md	Documented new params

Note

All of this code was written with Claude Code. I reviewed it and tested against a live server.