search_messages

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

Annotations provide readOnlyHint=true, and the description reinforces the read-only nature by framing it as a search. The description adds the public-only scope constraint and the count cap (1-100, default 20) which the annotation doesn't cover. For a read-only search with good annotation coverage, this is solid supplemental disclosure.

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

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

The description is compact and front-loaded with the key differentiator ('PUBLIC channels only') in the first sentence. The Args section is brief and readable. Slightly redundant (the default 20 appears twice, in counting and in args), but otherwise tight with no wasted prose.

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

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

An output schema exists, so return-value documentation isn't required. The tool is simple (2 params, one required) and the description covers purpose, scope limitations, and parameter semantics fully. For a filtered-search tool with readOnlyHint and an output schema, this is adequately complete.

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

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

Schema description coverage is 0%, so the description must compensate for parameter meaning. It does: 'query' is explained with concrete examples (ticket key, PR URL, keywords), and 'count' is documented with range and default. This fully covers the semantic burden of both parameters despite zero schema descriptions.

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

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

The description states a specific verb+resource ('Search Slack messages') with a clear scope restriction ('in PUBLIC channels only'). It explicitly differentiates itself from siblings by noting DMs and private channels are excluded, distinguishing from read_channel_history and read_thread which cover private/thread content.

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

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

Provides explicit usage context: 'Use this to find discussions about a Jira ticket or PR' with concrete query examples (ticket key, PR URL, keywords). It states the exclusion clearly ('Results from DMs and private channels are never returned'), guiding the agent away from using this tool for private-channel lookups. This is near-explicit when/when-not guidance.

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