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

Annotations already cover safety (readOnly=false, destructive=false, openWorld=true, idempotent=false), and the description adds real context beyond them: the 20-item cap and "All arrive or none do" atomicity, which is exactly the kind of behavior an agent needs before committing. It does not state what happens on repeat sends (duplicates, given idempotentHint=false) or what is returned 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?

Three short sentences: what it does, the permission gate with the recipient constraint, then the atomicity guarantee. Front-loaded and every clause carries information.

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 2-parameter mutation with full schema coverage and annotations, the description supplies the cap, atomicity, and user-consent gate, which is nearly everything needed to call it correctly. No output schema exists and the description says nothing about the return value or post-share verification, which is the remaining gap.

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 100%, so email and bubble_ids semantics, including the id pattern and the "from list_bubbles" provenance, are already documented in the schema. The description only echoes the cap and the exactness of the address, adding negligible meaning beyond the structured fields; baseline 3 applies.

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 first sentence states a specific verb (send copies), the resource (the user's bubbles), the target (another Sixteen Bridges account), the channel (email), and the cap (up to 20). The word "copies" distinguishes it from sibling mutators like delete_bubble, restore_bubble, and save_bubble without needing 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?

"Only when the user asks, to the exact address they give" is an explicit when-to-use gate plus a hard constraint on the recipient, which is unusually strong guidance. What's missing is naming any alternative (e.g., list_shares to inspect existing shares or a non-email flow), so it stops short of a 5.

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