thread

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

Goes well past the readOnlyHint by clarifying that nothing is marked as read, which is the non-obvious behavior for an email reader. It also discloses search scope (Inbox, Sent, Archive, Drafts, plus other mailboxes participating in the conversation) and error behavior for wrong or moved IDs.

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 the core action and result shape, and nearly every sentence carries new information (ordering, scope, safety, error). The mailbox-scope sentence is slightly convoluted but still 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?

For a single-parameter read tool with an output schema and readOnly/openWorld annotations, the description covers everything needed: what is returned, ordering, search scope, side-effect status, and failure mode. No material gap remains.

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% and the schema already documents message_id with an ID format example, so the baseline is 3. The description adds genuine value by clarifying that any message in the conversation is acceptable and that a wrong or moved ID produces an error.

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 (Read), resource (the whole conversation/thread of one email), and precise scope (oldest first, full plain-text bodies, attachment IDs). It is immediately distinguishable from siblings like emails and search, which only locate messages rather than expand a thread.

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: 'Use it to read an email that emails or search found,' and tells it to open attachments via the attachment tool. That names both the prerequisite (a found email) and the downstream alternative for attachment content.

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