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

Annotations mark this as non-read-only but non-destructive, and the description adds real context beyond them: the action makes your work visible to the flow's owner in their chat rail, which is a meaningful side effect. It still omits whether the attach requires ownership, is idempotent, or can be detached.

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?

Two tight sentences, with the primary action front-loaded ahead of the secondary tip about log_message. The parenthetical is helpful rather than filler, though the sentence is slightly dense.

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?

With no output schema and only thin annotations, the description covers the main effect but leaves gaps an agent would want: the meaning of the 'agent' parameter, behavior when already connected, and any permission requirements.

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%, so the description must carry parameter meaning. It implies flowId via 'EXISTING flow' but says nothing about the 'agent' parameter, leaving half the inputs undocumented in both schema and prose.

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 gives a concrete verb and resource ('Attach this agent session to an EXISTING flow as a chat in the builder's rail') and states the visible effect. It differentiates from creation siblings by capitalizing EXISTING, though it never names flow_create_flow as the contrasting tool.

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 rather than stated: the emphasis on 'EXISTING flow' steers away from creating a new one, and the tool points at log_message for narration. There is no explicit when-not-to-use, no prerequisite (e.g. needing a valid flowId or ownership), and no stated alternative for starting fresh.

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