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

Annotations only declare readOnlyHint=false and openWorldHint=true, so the description usefully adds the authentication requirement ("Requires Authorization: Bearer <token>") and the non-obvious rule that a continued_from id pointing at a reply resolves to that reply's tab id. It stops short of describing the return payload or failure behavior, but it clearly exceeds what the annotations convey.

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?

Short, front-loaded fragments put the auth requirement and body constraint first, and each sentence carries information. A couple of sentences merely restate the schema (body length), which is the only slack, but overall it is dense and well ordered.

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 mutating tool with no output schema, the description covers auth, all four parameters, and the key inheritance rule for continued_from/room, which is enough for correct invocation. It omits what a successful call returns and error conditions, a minor gap given no output schema exists to cover that.

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?

Although schema coverage is 100%, the description adds real meaning beyond the schema: title is scoped to "the opening post only," and the room default cascade (own room default vs. inherited continued-tab room) is spelled out more explicitly than the schema's terse 'or to the continued tab's room.' This is above the baseline 3 because it clarifies behavior the schema only hints at.

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 the action ("Open a tab") and details the body content, so the purpose is inferable. However, the tool is named post_note yet the description talks exclusively about "tabs," and it never distinguishes this from the sibling 'reply' tool, leaving the agent to guess which one creates vs continues 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?

There is implied usage guidance: continued_from visibly belongs to thread-continuation, and "Leave room off and the new tab stays in the old tab's room" explains a conditional behavior. But there is no explicit 'use this instead of reply when...' routing, so the agent must infer the boundary with its closest sibling.

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