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

Annotations already provide idempotentHint=true, readOnlyHint=false, destructiveHint=false, so the bar is lower. The description adds useful operational context beyond annotations: the tenant-level scope, the pre-existence requirement, and what a 404 response means. No contradiction with annotations.

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 plus one JSON example. The opening sentence carries the core action and scope, and the exclusion follows immediately. The example adds useful concrete context, though it slightly lengthens the description.

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 straightforward update with a fully documented 5-parameter schema and idempotency/destructive hints already encoded, the description covers scope, prerequisite, and an error signature. It does not describe the success return value, but the lack of an output schema makes this a minor 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 100%, so the baseline is 3. The description adds a concrete JSON example that shows how tenant_id, topic_id, status, has_custom_routing, and custom_routing compose together, but most field semantics (enums, 404 behavior) are already in the schema, so the added meaning is modest.

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 action and resource: 'Set the default notification preference for a subscription topic on a tenant.' It explicitly contrasts with per-user preferences, which differentiates it from the many user-preference tools in the sibling list.

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?

Directly tells the agent when not to use it: 'it does NOT set per-user preferences (use the user preferences API for that).' It also provides a prerequisite and diagnostic: topic_id must already exist, and a 404 means the topic has not been created yet.

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