get_thread

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context: the sorting order (date_received ascending), the underlying dispatch mechanism (tiered IMAP threading vs. AppleScript path), and a concrete limitation about missed threads when subject rewrite occurs on the AppleScript fallback. This goes well beyond the annotations and helps the agent anticipate edge cases.

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 logically structured: it starts with the primary purpose, then explains the lookup mechanism, provides usage guidance, and ends with a known limitation. It is a bit longer than necessary but each sentence carries useful information. The front-loaded purpose makes the key intent immediately clear. It earns a 4 for effective organization despite slight verbosity.

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?

Given that an output schema exists to define the return structure, the description does not need to explain return values. It covers the essential behavioral details (sorting, fallback paths, limitation) and provides integration suggestions. While it doesn't mention empty results or error conditions, these are typically not critical for a read-only retrieval tool. Overall, the description is complete enough for an agent to call the tool correctly and interpret the outcome.

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?

The single parameter message_id is fully documented in the schema (100% coverage), including the note that it is an 'Internal id of any message in the thread (from search_messages or get_messages results).' The description does not add any additional meaning beyond the schema; it simply mentions the anchor message without elaborating on format or constraints. Since the schema already covers semantics, a baseline score of 3 is appropriate.

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 opens with a precise statement: 'Return all messages in the thread containing the given message.' This specifies a clear verb (return), a distinct resource (thread), and a scoping condition (containing the given message). It is easily distinguishable from siblings like get_messages (which likely fetches specific message IDs) and search_messages (which searches by criteria), so an agent can select it without ambiguity.

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?

The description provides explicit follow-up guidance: 'The returned ids can be piped into search_messages(source=[ids]) for filtered metadata or get_messages([ids]) for full bodies.' This tells the agent what to do with the output, which is valuable. It does not explicitly state when NOT to use this tool versus alternatives, but the threading focus and the pipe suggestions imply the intended use case. The known limitation also helps set expectations.

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