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

Annotations already disclose a non-read-only, non-open-world, destructive operation, but the description does not explain what is destructive or what side effects posting creates. It adds an authorization constraint ('currently authorized private Space') and a cryptic delivery caveat ('shared seen state does not prove receipt'), but omits key behavior such as idempotency handling and visibility.

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 short and front-loads usage, but the second sentence is cryptic and does not clearly help an agent call the tool. Phrases like 'Reply and mention continuations belong to this task' and 'shared seen state does not prove receipt' consume space without clarifying required behavior.

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?

This is a five-parameter write tool with a destructive annotation, low schema description coverage, and no description of idempotency, channel or title semantics, or side effects. An output schema exists, so return values need not be explained, but the definition still leaves too much unsaid for safe and correct invocation.

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 low at 20%, so the description should compensate for undocumented parameters. It adds no meaning for title, channel_id, space_id, or especially idempotency_key, which is required and non-obvious; only the general private Space context loosely relates to space_id.

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 says to use 'post thread' within a private Space, which gives a vague action/resource/scope but does not explicitly state that it creates a new thread. It also does not clearly distinguish itself from the sibling private_space_post_reply, and the phrase about replies and mentions belongs to this task adds ambiguity.

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?

The only usage context is 'within one currently authorized private Space,' with no explicit when-to-use versus when-to-use-alternatives guidance. The sibling private_space_post_reply is not named or compared, leaving the agent to infer whether this tool creates a thread or posts into one.

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