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

Adds meaningful context beyond the annotations: it discloses a side effect ('clears the active site') and the authorization requirement, neither of which appears in the structured fields. The readOnlyHint=true annotation is in mild tension with a session-state mutation, but since no persistent resource is modified, this is not a contradiction.

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?

One compact sentence with a semicolon-delimited structure: the action and session scope come first, the side effect second, and the permission constraint last. Nothing is wasted.

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 single-parameter, non-output tool, the description covers the action, its session-wide effect, the side effect on the prior site selection, and the access constraint. An agent has everything needed to invoke it correctly.

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% and the single 'slug' parameter is fully documented in the schema, so the baseline is 3. The description adds no format or validation detail beyond what the schema already provides.

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 and resource ('Make a template the edit target for this session') and immediately scopes the downstream effect ('editing tools then act on it'). It also distinguishes itself from the site-selection sibling by noting it 'clears the active site', so an agent can tell it apart from select_site without opening either 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?

Gives clear context for use (prior to editing tools that operate on a template) and states the permission gate (admin or tenant owner/editor). It stops short of naming the alternative (select_site) as an explicit either/or, so the routing decision is implied rather than spelled out.

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