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

With no annotations, the description carries the full burden for behavioral disclosure. It does reveal the 280-character limit, which is a useful constraint. However, it omits critical behavioral traits such as authentication requirements (api_key), whether the message is appended or overwrites, and any side effects on the planet wall.

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 description is a single sentence with no unnecessary words. Every element—action, target, constraint—contributes to understanding the tool. It is front-loaded with the verb and critical 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?

Given the tool has 3 required parameters, no annotations, and no output schema, the description is too sparse. It does not specify how api_key is used, whether there are any restrictions on which planets can receive messages, or what the response/return behavior is. This leaves the agent with significant uncertainty about how to correctly invoke and interpret results.

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 0%, so the description must compensate. It adds meaning to the 'message' parameter via the 280-char limit and implies that 'slug' identifies the planet ('any planet's wall'). However, the 'api_key' parameter is not explained at all, leaving a gap in parameter understanding.

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 the action 'Leave a message' with a specific target ('any planet's wall') and a constraint (max 280 chars). This distinguishes it from sibling tools like build or claim_planet, which are all different operations.

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 phrase 'on any planet's wall' implies when to use the tool, but the description does not explicitly discuss when to use it versus alternatives (e.g., visit_planet) or any exclusions. No clear context or when-not-to-use guidance is provided.

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