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

Annotations only declare the generic profile (readOnly=false, destructive=false, non-idempotent). The description adds real context beyond that: the session is private and expiring, the token grants access and must not be published, and one session can hold multiple designs and a team basket.

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?

Front-loaded with the core action, then the token-handling and scoping details. Four short sentences, each carrying distinct information (action, retention, security, capacity); no filler.

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?

With no params and no output schema, the description usefully names the two key return values and the session lifecycle (expiring) plus token sensitivity. It stops short of describing expiry behavior or failure modes, but for a parameterless creator this is close to complete.

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?

Zero parameters and 100% schema coverage, so the baseline is 4. The description references returned values (subject, sessionToken) rather than inputs, which is appropriate since there is nothing to parameterize.

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 (Start) plus resource (design session) and adds distinguishing scope: private, expiring, guest. An agent can tell this apart from end_design_session and get_design_session without opening a 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?

The line about keeping subject/sessionToken 'for every follow-up' implies this is a prerequisite step for later calls, but no alternative or when-not condition is named (e.g., vs get_design_session or end_design_session). Usage is implied rather than stated.

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