List all registered Compass sessions

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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint=false, so the safety profile is covered. The description goes well beyond that, disclosing the empty/null return state and the non-obvious semantics that the registry does not change request routing, which an agent could not infer from structured fields.

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 sentences, each carrying distinct information: the return shape, the empty/null edge case, and the crucial routing caveat. The core purpose is front-loaded and no sentence is redundant.

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?

No output schema exists, so the description must carry return-value meaning, and it does by naming sessions and active_session_id plus their empty/null behavior. Combined with annotations covering the read-only idempotent profile, nothing needed to invoke or interpret this tool is missing.

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?

The tool takes zero parameters, so the schema has nothing to document and the description correctly spends no words on inputs. Baseline 4 applies for a no-parameter tool; there is no parameter ambiguity to resolve.

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 gives a specific verb (list) and two concrete resources (registered account labels and active_session_id), so an agent knows exactly what is returned. It does not explicitly name sibling tools like compass_register_session or compass_set_active_session to sharpen the boundary, but the scope is unambiguous on its own.

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 description conveys the operative context: that the session registry is a label only and does not affect which account Compass requests use, and that switching accounts requires signing the browser tab in. That is real usage guidance, though it never states a direct 'use this when...' rule or names an alternative tool.

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