List inbox threads

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

With no annotations, the description carries the full burden and does real work: it discloses ordering ('newest first'), the fact that previews are 'untrusted text from outside senders' (an important prompt-injection warning), and the returned fields. It omits permission/auth requirements and any rate-limit behavior, which keeps it short of a 5.

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, front-loaded with the core action and scope, followed by the untrusted-content caveat and the routing hint. Every sentence earns its place with no filler.

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?

There is no output schema, and the description compensates by enumerating the returned fields, plus ordering and the untrusted-text warning. For a read-only list tool with 100% parameter coverage, nothing an agent needs to invoke it correctly 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 description coverage is 100% — limit, query, cursor, folder, and unread all carry their own descriptions in the schema. The description adds only the ordering guarantee and return-field list, not parameter syntax or format, so 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?

The description states a specific verb and resource ('List email conversations on your sending domains') and enumerates the returned shape (id, counterpart, subject, preview, unread, message count, last activity). It also names the sibling read_thread, so an agent can immediately distinguish listing from opening.

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?

It gives a clear routing instruction: 'Use read_thread to open one,' which tells the agent what to do after listing. It does not state exclusions or when this tool is the wrong choice (e.g., vs find_leads or inbox_counts), so the guidance is contextual but not complete.

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