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

Beyond the read-only, non-destructive annotations, the description discloses important behavior: it returns only an opening_excerpt of up to 240 Unicode characters, not the full opening. It also explains that the cursor pages this enumeration rather than new activity or received replies, and warns that creation order can miss recent replies on older threads beyond the current page.

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?

The description is front-loaded with the core operation and scope, then adds output limitation, pagination semantics, and the ordering caveat. Every sentence contributes practical invocation guidance without redundant restatement of the title or annotations.

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?

Given that an output schema exists, the description need not fully document return values, but it helpfully explains opening_excerpt and has_more. It covers authorization scope, ordering, pagination, and the key caveat about missing recent replies on older threads. The main remaining gap is that it does not explain the limit parameter or explicitly disambiguate from active/followed thread list siblings.

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 0%, so the description must carry parameter meaning. It clarifies that space_id and channel_id scope the request to one authorized private Space and channel, and it explains cursor as the pagination mechanism. However, it does not describe limit behavior or ID format expectations, leaving some schema parameters semantically thin.

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 thread previews in one authorized private Space and channel, ordered by newest creation first. It also distinguishes this enumeration from private_space_read_thread and clarifies that the cursor pages creation order rather than new activity or received replies, which separates it from active-thread listing.

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 clear usage guidance for previews versus full content by naming private_space_read_thread as the alternative when full content is needed. It also explains pagination behavior and the caveat that creation-order listing can miss recent replies on older threads. It stops short of explicitly naming active-thread or followed-thread list tools as alternatives.

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