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

Annotations already declare this is a non-destructive, closed-world read, so the safety profile is covered. The description adds real behavioral context beyond that: thread reconstruction is done via Message-ID/References, replies from the Sent folder are included, results are ordered oldest first, and the payload is uids rather than bodies.

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?

Two sentences, zero filler, with the core action front-loaded and the follow-up tool hint placed second. Every clause earns its place.

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 no output schema, the description carries the burden of describing returns, and it does so adequately by stating that uids are returned, ordered oldest first, and need a follow-up read_message call for bodies. It is silent on edge cases such as messages whose headers lack References, which is a minor gap.

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 100% and each of the three parameters is documented in the schema (uid as 'any message in the conversation', folder default INBOX, full mailbox address). The description adds the concept that the uid may be any message in the thread, but nothing about the folder/mailbox interaction, so it sits at the baseline for high schema coverage.

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?

States a specific verb (reconstruct) and resource (the whole conversation a message belongs to), and names the mechanism (Message-ID/References). It also implicitly distinguishes itself from read_message by noting it returns uids rather than bodies, so an agent can tell the two apart without opening either schema.

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?

Explicitly routes the agent to read_message for full bodies of the returned uids, which is a clear when-to-use-next instruction. It does not, however, contrast itself against search_messages or list_messages, which also surface messages, so the exclusion set is incomplete.

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