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

No annotations are provided, so the description carries the behavioral burden. It discloses useful traits: markdown support, an 8KB size limit, and reply_to threading. It omits side effects like auth requirements or visibility, but the essential behavior is covered.

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 short sentences, no filler. The main action is front-loaded and every detail in the description contributes to understanding, invocation, or constraint.

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 3-parameter mutable tool with no output schema, the description is mostly complete. The only notable gap is not stating whether the action returns anything or what the response format is, but the inputs and constraints are sufficient for initial 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?

Schema documentation covers all three parameters. The description adds meaningful semantics by indicating the body supports markdown and is limited to 8KB, and by clarifying that reply_to enables threading. The space parameter is not expanded, but the overall parameter semantics go beyond the schema.

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?

Clearly states the verb 'Post', the resource ('message to a space'), and key constraints (markdown, ≤8KB). No sibling tool overlaps with this exact action, so an agent can immediately distinguish it.

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 conveys the core situation for use but does not explicitly define when not to use it or mention alternatives such as create_artifact or edit_artifact. Usage context is implied rather than explicitly routed.

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