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

Annotations already declare readOnlyHint=false, idempotentHint=false, and openWorldHint=true, so the safety profile is mostly covered. The description adds an important operational constraint beyond annotations: at most one call per thread every 2.5 seconds, and extra calls return 'skipped'. It does not describe the normal successful return value, which keeps it from being 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 description is two concise sentences and front-loads the core purpose before the rate-limit detail. Every sentence earns its place, with no redundant restatement of the title or annotations.

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 simple fire-and-forget typing indicator, the description covers the main purpose and an important rate-limit behavior. However, it leaves threadId semantics undocumented and does not clarify normal return behavior, which is relevant because no output schema exists. It is adequate but incomplete for reliable invocation.

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?

There is only one parameter, threadId, and schema description coverage is 0%. The description says 'per thread' and 'conversation', which loosely connects threadId to a conversation, but it does not explain the expected format (CUID2), where to obtain the ID, or any constraints. With low schema coverage, the description does not compensate.

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 a specific verb and resource ('Send typing indicator') and immediately explains the visible effect ('Shows the account link as typing in the conversation'). This distinguishes it from all sibling tools, which deal with messages, threads, or account links rather than live typing status.

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?

Usage is implied by the purpose and by the rate-limit note, but the description does not explicitly say when to call this versus alternatives like messages_send or threads_update. There are no stated prerequisites or exclusions, so the agent must infer the appropriate context.

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