get_thread

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint. The description adds significant behavioral details: tiered IMAP threading dispatch algorithm, AppleScript fallback, sorting by date_received ascending, and a known limitation about missed members on the fallback path.

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 well-structured into three clear paragraphs: purpose, algorithm/sorting, and usage suggestion plus limitation. Each sentence adds value without redundancy.

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?

With an output schema present, the description need not explain return values. It covers the tool's behavior, internal algorithm, and a known limitation. For a read-only threading tool, this is fully adequate.

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 coverage is 100% with a description for message_id. The description restates that it's an internal ID but adds context about looking up the anchor message. This provides marginal added value beyond the schema, meeting the baseline of 3.

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 explicitly states it returns all messages in a thread given a message ID, with specific verb 'Return' and resource 'thread'. It distinguishes from siblings like get_messages and search_messages by explaining how the returned IDs can be piped into those tools.

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 clear context on when to use (to get a thread), how the lookup works, and what to do with the results. Does not explicitly state when not to use but offers alternatives like search_messages and get_messages.

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