Read a conversation

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

Annotations already declare readOnlyHint and openWorldHint=false, and the description adds genuinely new behavioral detail: cross-folder aggregation, oldest-first ordering, quoted history being cut off, and participant counts with message counts. It doesn't discuss truncation limits or rate/permission behavior, but the added output-shaping context is substantial.

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?

A single front-loaded sentence that leads with what is returned, then layers scope, ordering, and trimming. Every clause carries information; nothing is redundant or padded.

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, return-value explanation isn't required, and the annotations cover the safety profile. The description supplies scope, ordering, and trimming behavior; the only minor gap is what happens when a thread exceeds max_messages, which the schema parameter partially addresses.

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%, so all three parameters (message_id, max_messages, max_chars_per_message) are already documented in the schema. The description's mention of 'quoted history cut off' and 'oldest first' loosely relates to the char/message limits and ordering, but adds no syntax or default detail beyond the schema — the baseline 3 applies.

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 and resource — retrieving the 'whole email conversation the message belongs to' — with scope details (across Inbox, Sent and other folders, oldest first, quoted history trimmed). This clearly separates it from get_message (one message) and search_messages (matching messages) without needing to name them.

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?

Gives clear use-case context: 'everything needed to summarize a thread, see who said what, and find open questions.' It doesn't name an alternative tool or state when not to use it, so it stops short of full routing guidance.

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