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jtalk22

Slack MCP Server

by jtalk22
OverviewSchemaSourceRelated ServersDiscussionsAdmin
JavaScript
Hybrid

slack_search_messages

Read-onlyIdempotent

Search Slack messages across the workspace by query to find specific conversations, using filters like from:@user or in:#channel.

Instructions

Search messages across the Slack workspace

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
countNoNumber of results (max 100, default 20)
queryYesSearch query (supports Slack syntax like from:@user, in:#channel)
provenanceNoAuthor labelling for returned messages. label (default) stamps origin and author_trusted on every message; strict also holds slack_send_message after outside-authored text has been read. Defaults to SLACK_MCP_PROVENANCE, else label. This argument can only tighten labelling, never loosen it: to drop the labels entirely and get the pre-5.1 output shape, set SLACK_MCP_PROVENANCE=off on the server.
include_rich_message_fieldsNoInclude Slack message attachments, blocks, metadata, files, and reactions when present

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv5.1.0
    • addedInput schema / properties / provenance
      Added value: +{
+  "description": "Author labelling for returned messages. label (default) stamps origin and author_trusted on every message; strict also holds slack_send_message after outside-authored text has been read. Defaults to SLACK_MCP_PROVENANCE, else label. This argument can only tighten labelling, never loosen it: to drop the labels entirely and get the pre-5.1 output shape, set SLACK_MCP_PROVENANCE=off on the server.",
+  "enum": [
+    "off",
+    "label",
+    "strict"
+  ],
+  "type": "string"
+}
  2. First observedv4.4.0

TDQS

C2.9/5.0
Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the safety profile is covered structurally. The description adds nothing beyond them — no note on result volume/caps, no mention that this hits Slack's search index (which has indexing lag/limited retention), and no hint about the provenance/labelling behavior governed by the schema's provenance parameter.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

A single efficient sentence with the resource and scope front-loaded and zero filler. It is arguably too terse to be fully 'appropriate', but nothing in it is wasted.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With rich annotations and 100% schema coverage, the description is minimally sufficient to call the tool correctly. However, for a search tool with no output schema it omits anything about result shape, pagination/truncation at the 100-result cap, or how it relates to the conversation-scoped retrieval siblings.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so all four parameters (count, query, provenance, include_rich_message_fields) are already documented in the schema, including Slack query syntax and the provenance tightening rules. The description adds no parameter-level meaning beyond that, so the baseline of 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

Specific verb+resource ('Search messages') with an explicit scope ('across the Slack workspace'), so the agent knows this is a cross-workspace text search rather than a per-conversation fetch. It stops short of distinguishing itself from siblings like slack_conversations_history, slack_get_full_conversation, or slack_catch_me_up.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives no when-to-use guidance, no prerequisites, and never names an alternative among the many overlapping retrieval siblings (slack_conversations_history, slack_get_thread, slack_catch_me_up). The only routing signal is the implicit 'across the workspace' scope, which the agent must infer.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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