Read a conversation

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

Annotations already declare readOnlyHint and openWorldHint=false, so the safety profile is covered and 'Read-only' is redundant. The description still adds real behavior beyond the annotations: oldest-first ordering, the shared max_chars budget split evenly with a 2,000-character floor per message, '[truncated]' marking for cut bodies, and an error on unknown thread_id. The only gap is the shape of that error response, which is minor.

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?

Front-loaded with what is read and in what order, then selection guidance, then the truncation rule and error behavior. No filler sentences, and each clause contributes a distinct fact an agent needs.

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?

For a three-parameter read tool with no output schema, it covers ordering, field parity with read_email, truncation semantics, and failure on a bad thread_id. Nothing an agent needs in order to call it correctly or interpret the result is missing.

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 the baseline is 3, but the description goes further by clarifying that max_chars applies across the whole thread rather than per message and that each message gets an equal share with a 2,000-character minimum. That resolves the main ambiguity an agent could hit when setting the value.

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 — 'Read a whole conversation: every message in the thread, oldest first' — and pins the return shape by reference ('same fields as read_email'). It explicitly separates itself from the closest sibling, read_email, so an agent can choose 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?

Gives both a positive condition ('when the reply history matters, such as before answering or summarising a back-and-forth') and an explicit alternative ('use read_email for a single message'). The routing decision is fully specified rather than implied.

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