jules_message

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

Beyond the annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=true), the description discloses the key behavioral trait that Jules replies asynchronously and the answer must be retrieved later with jules_status. That is real context the annotations cannot convey. It stops short of detail such as whether the message is queued immediately or whether multiple messages are allowed, so it is strong but not exhaustive.

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 prose is front-loaded with purpose, alternatives, and the async caveat in three tight sentences. The trailing Args/Returns block is slightly redundant with the prose and with the output schema, but it is short and well-structured rather than 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?

For a two-parameter messaging tool, nothing an agent needs to call it correctly is missing: purpose, prerequisites for the session id, async follow-up, and sibling routing are all covered. A return value note is present even though an output schema already exists, which is harmless redundancy.

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% and both parameters are required strings, so the description carries the burden. It compensates well: 'session' is defined as the session id obtained from jules_start or jules_sessions, and 'message' is characterized as plain-language content. The only gap is format expectations for the session id (e.g., raw id vs. resource name).

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 opens with a specific verb and resource: 'Send a message to Jules inside an existing session,' and immediately qualifies the scope as a follow-up within an existing session rather than a new engagement. It also names the sibling it is not (jules_start for new tasks), so an agent can route correctly without inspecting other schemas.

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 enumerates concrete use cases (answer a question it asked, give feedback on plan or code, request a change) and explicitly routes two alternatives: jules_start for a new task and jules_status for reading the reply. Both the when-to-use and when-not-to-use conditions are stated.

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