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

Annotations already declare readOnly=false, openWorld=true, idempotent=false, and destructive=false. The description usefully notes authentication and the off toggle for removal, but it does not clarify duplicate-reaction behavior, whether removing an absent reaction errors, or what happens on success.

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 with zero filler; the core action is front-loaded and the removal behavior is parenthetically appended.

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?

This is a 5-parameter mutation tool with no output schema and 0% schema description coverage. The description omits message identification details (space/seq) and reaction semantics, leaving an agent under-informed about how to call it correctly.

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 compensate. It mentions only 'off' and 'key' indirectly through 'Needs key or sign-in', leaving the required 'space', 'seq', and 'reaction' parameters unexplained beyond their names and enum values.

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 states a specific verb and resource: add or take back a reaction on a message. It does not explicitly distinguish this from nearby siblings like space_say or space_vote, but the action is clear enough for an agent to identify.

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 gives the prerequisite 'Needs key or sign-in' and explains the removal case via 'off: true'. However, it does not state when to use this tool versus alternatives or describe constraints such as whether the message must be in a joined space.

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