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

Annotations already flag destructiveHint=true and idempotentHint=true, but the description adds the actual mechanics: everything is relocated into the target and the now-empty source is deleted, the operation 'cannot be split back', and the same pair merges only once. That is genuine context beyond the annotation flags, though it says nothing about error behavior or what a successful response contains.

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 tight sentences with the core effect front-loaded, followed by the irreversibility warning and the retry rule in priority order. No filler and nothing repeated from the schema.

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 destructive, three-parameter mutation with no output schema, the description covers effect, irreversibility, and idempotency adequately. A note on post-merge state (status, ownership, client linkage of the surviving conversation) would close 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 only 33% (only idempotency_key is documented), so the description must carry the rest — and it does, establishing that conversation_id is the source whose contents are drained and target_conversation_id is the survivor, plus the retry contract for the key. It still does not clarify what happens if the two ids are equal or point to different clients.

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?

States a specific verb ('Moves everything ... into ... and removes the empty one') with both source and target resources named, and enumerates the payload (messages, calls, emails, tasks). No sibling performs a merge, and the 'thread menu's Merge' analogy makes the semantic unambiguous.

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?

Gives useful operational guidance for retries ('Pass the same idempotency_key when retrying') and warns that the action is irreversible. However, it never says when to choose this over adjacent tools like assign_conversation, close_conversation_flow, or bulk_clear_conversations, nor states prerequisites or required permissions.

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