Register a signed-in Compass session

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

Beyond annotations (idempotentHint=true), the description discloses important behavior: re-registering the same account_identity updates rather than duplicates, the first registered session becomes the default active_session_id, and the call returns session_id for routing. These are non-obvious and valuable for correct invocation.

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 concise, front-loaded with the core purpose, and every sentence adds necessary information about refresh behavior, return value, default active behavior, or mark_active usage. No filler or redundancy.

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 tool with no output schema, the description provides the essential contract: return value, idempotent refresh behavior, default active session semantics, and how to mark active. Required parameter context is covered by the schema, and the description fills behavioral gaps.

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 the baseline is 3. The description adds meaningful semantics for account_identity (keyed identity, refresh behavior) and mark_active (can set active in the same call), enriching the schema's raw definitions.

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?

Description states a specific action ('Register (or refresh)') on a specific resource ('authenticated Compass session keyed by signed-in account identity') and clarifies the keying mechanism. It clearly differentiates from siblings like compass_set_active_session by describing session creation/update semantics and the mark_active option.

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?

Provides clear context for when to call: to register or refresh a session keyed by identity, with re-registration updating the existing session. It also explains when to pass mark_active: true, but does not explicitly name alternatives like compass_set_active_session or state when not to use this tool.

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