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

Annotations already state this is non-destructive and not open-world; the description adds the valuable non-structured detail that the call blocks for up to ~25 seconds and can return degraded states (stillLearning, empty sources) with prescribed remediation. It does not say whether the sent message persists in the preview conversation or how failures surface, keeping it below a 5.

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 core action is front-loaded, but the remainder is a dense run-on chain of branches with awkward phrasing ('When `sources` is empty otherwise') and undefined terms (stillLearning, sources, 'the minutes it gives') that make it harder to parse than it needs to be.

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?

An output schema exists, so return values needn't be enumerated, and the description instead explains how to interpret key output states and what to do next. For a 3-parameter, non-destructive call with full annotation coverage, nothing critical is missing, though the undefined 'pending'/'sources' references leave slight ambiguity.

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 100% and already documents all three parameters (text as the customer's message, agentId from list_agents, conversationId from test_agent). The description adds no additional meaning about parameter formats or constraints beyond the schema, so the baseline 3 applies.

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?

States a specific verb+resource ('send a follow-up message in a preview conversation test_agent started') and explicitly anchors itself to the sibling test_agent, so an agent can tell this is the second-turn continuation rather than a new test. The 25-second wait behavior is stated up front.

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?

Gives explicit conditional routing: use list_messages (don't ask again) for a pending answer, use add_knowledge_article then retest when stillLearning or when sources is empty. The only friction is the reference to 'pending: true', which is not an input parameter in the schema and could be misread as something to pass; otherwise the when/when-not guidance is unusually complete.

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