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

Annotations already declare readOnlyHint=false and destructiveHint=true, so the write/mutation nature is covered. The description adds genuinely non-redundant context: no draft mode, the confirm gate, and that the post appears under the connected user's identity rather than the agent's — that identity disclosure is behaviorally important and not in the structured fields.

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?

Three compact sentences, front-loaded with the core action, then the confirm constraint, then the identity caveat. Every clause carries information and nothing is repeated from the schema verbatim.

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 write tool with annotations and no output schema, the description covers the critical invocation constraint (confirm), the identity semantics, and the no-draft behavior. It leaves out error/rate-limit behavior and the meaning of bodyContentType, but the essentials an agent needs to call it correctly are present.

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 only 50% (teamId, channelId, confirm documented; body, subject, bodyContentType have none). The description adds no meaning for the undocumented parameters — it never explains body formatting, the text/html choice, or subject — so it fails to compensate for the coverage gap.

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 and resource ('Post a message to a Microsoft Teams channel') and names the acting identity, which cleanly separates it from siblings like send_outlook_message, create_comment, or create_teams_message. An agent can identify the operation and the target surface without opening 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?

It communicates that there is no draft path and that confirm=true is mandatory, which implies this is the right tool only when an immediate, confirmed send is intended. However, it never names alternatives (e.g. send_outlook_message for email) or states explicit when-not-to-use conditions, so the routing guidance is only implied.

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