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

Goes well beyond the annotations: it discloses that the indicator is VISIBLE to the counterpart, that it is ephemeral and sends no message, and that the call is approval-exempt yet authorized, rate-limited and logged. The annotations only say non-read-only, idempotent, open-world, non-destructive; the description supplies the operational and social consequences the agent actually needs.

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?

Four short sentences, front-loaded with the action and followed by visibility, ephemerality and authorization facts in order of importance. Every clause carries distinct information; nothing repeats the annotations or the schema.

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?

Low-complexity tool with an output schema, so return values need no explanation. The description covers visibility, side effects, authorization, rate limiting and logging, which is everything an agent must know before invoking it.

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 67% and the schema itself explains the presence enum values and the duration_seconds meaning (single pulse when omitted). The description adds no per-parameter detail and says nothing about the ^\d+$ constraint on conversation_id, so it does not exceed the schema baseline.

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 first sentence gives a precise verb and resource: 'Show (or stop) a typing/recording indicator in a conversation.' It also captures the toggle semantics ('or stop') that no sibling tool covers, so an agent can identify it instantly among the list/draft/update tools.

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?

Explicit when-to-use ('only immediately before an actual reply') and an explicit prohibition ('never to simulate attention'), which is exactly the kind of guardrail an agent needs for a visible-side-effect tool. No alternative routing is needed because no sibling overlaps this function.

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