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

Annotations already declare this is a mutation (readOnlyHint=false) and non-destructive, so the safety profile is covered. The description adds genuinely useful behavior beyond that: 'Only the keys given change' establishes merge/patch semantics, which is not conveyed by idempotentHint or destructiveHint alone.

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 short, front-loaded sentences: purpose first, the partial-update rule second, the key list last. The key enumeration mildly duplicates the schema's property names, but it earns its place by pinning them to the `prefs` argument.

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-nested-object mutation with no output schema and adequate annotations, the description covers purpose, patch semantics, and the full accepted key set. The remaining gap is that it never indicates how to read current preferences back (get_notification_prefs), which an agent setting a partial update may want.

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 0%, so the description must carry the meaning, and it does: it names all seven accepted keys inside `prefs` and confirms the partial-update contract. It still doesn't add value semantics beyond key names (e.g., what 'tips' or 'monthlyReport' actually control), but it fully compensates for the missing schema descriptions.

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 names a concrete verb+resource ('Turns individual Blawgy notification emails on or off') and scopes it to the signed-in account, so the mutation intent is unambiguous. It does not explicitly name the read-side sibling get_notification_prefs, so the differentiation is inferable from the verb rather than stated.

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?

Usage is implied: use this to change notification email toggles. There is no explicit guidance on when to prefer it over get_notification_prefs for reading current values, and no mention of prerequisites or account/permission context, leaving the agent to infer routing.

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