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

Annotations already declare destructiveHint=true, idempotentHint=true, and openWorldHint=true. The description adds real value by spelling out the idempotency contract (same key returns the first result), which goes beyond the bare idempotentHint flag. It still omits what actually happens to the thread's messages, whether other participants are affected, and whether the leave is reversible.

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 short sentences with no filler, and the permanence constraint is front-loaded before the retry semantics. The first sentence's phrasing ("for good as one of your addresses") is slightly awkward but not wasteful.

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 destructive, open-world mutation with three required parameters, zero schema descriptions, and no output schema. The description covers only the idempotency key and leaves the agent guessing about parameter meaning, side effects, and results — insufficient for the tool's complexity.

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 0%: thread_id and as_address have no descriptions anywhere. The description only explains idempotency_key retry behavior, leaving two of three required parameters undocumented in both schema and prose.

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?

"Leave a thread" states a specific verb and resource, and "as one of your addresses" hints that the operation is scoped to the calling address. However, it never distinguishes this from the sibling delete_thread or archive_address, so an agent cannot tell from the text alone which removal semantics apply.

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?

There is no guidance on when to use this instead of delete_thread, archive_address, or simply stopping reads of the thread. The phrase "for good" implies permanence but no alternative or exclusion is named.

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