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

Annotations only declare readOnlyHint=false, openWorldHint=true, destructiveHint=false; the description adds genuinely new behavioral context: the default per-call confirmation flow (switchable off for this tool), the external-reach warning, and the Cotlet API key authorization requirement. It does not describe the return value or rate limits, but the confirmation and auth details go meaningfully beyond annotations.

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 purpose is front-loaded in the first sentence and the scope/consequence details follow. Slightly repetitive — the confirmation requirement is stated twice ('By default you confirm each call' and 'confirm with the user before each call') — but each sentence otherwise carries information.

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 mutation with no output schema, the description covers what is sent, where it lands, who sees it, the confirmation behavior, and the auth requirement. Only minor gaps remain, such as what a successful send returns or whether messages are editable/undoable.

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 100% and both parameters are documented in the schema, including that workstream_id comes from list_workstreams. The description adds no additional parameter syntax or constraints, so the baseline 3 for schema-covered parameters 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 message to the buyer in a WorkStream') and clarifies the scope: one WorkStream = one buyer and one project, so it cannot reach other buyers. This cleanly separates it from siblings like peopleperhour_send_proposal or peopleperhour_get_workstream without needing the schema.

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?

Provides context for use ('Posts a message in one WorkStream under your name') and an explicit confirmation condition ('Reaches other people: confirm with the user before each call'), but never names an alternative tool or explains when to choose this over other PeoplePerHour messaging/proposal actions. Usage is implied rather than fully routed.

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