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

Annotations already declare readOnlyHint=false and destructiveHint=false, but the description adds a meaningful behavioral detail: 'always labeled as agent activity.' It also reinforces that the operation targets an existing topic, implying a mutation. This goes beyond what annotations provide, though it does not detail side effects or reversibility.

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 sentences, front-loaded with the primary action and the key behavioral note. No fluff or redundant restating of the title. Every clause earns its place.

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 write action with no output schema, the description covers the essential selection criteria, source of the topicId, and the labeling behavior. Nothing an agent needs to decide whether to call it or to gather the required inputs is missing.

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% (two of three parameters have descriptions). The description adds value by clarifying that topicId comes from the board or post_board_topic's result, and reinforces that agentName is always labeled as an agent. Body remains undocumented, but min/max constraints are in the schema, so the added context is helpful and not redundant.

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 clearly states a specific verb ('Reply') and resource ('existing Message Board topic'), and explicitly distinguishes it from post_board_topic by emphasizing 'existing' and referencing post_board_topic's result. An agent can immediately tell this is for replying, not creating, 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?

The description tells the agent where to obtain the topicId ('from the board or from post_board_topic's result'), which implies the correct workflow and separates it from the creation tool. It lacks an explicit 'use this when' or 'do not use for X', but the context is clear enough to route correctly.

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