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

Annotations already declare write (readOnlyHint=false), non-destructive, and closed-world behavior, lowering the bar. The description adds the overwrite semantics ('Replace') and the per-project entry rule, but never explains what happens to prior entries, what 'key' controls, or what authorization is needed. Adequate but thin for a mutation.

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?

Two compact clauses, front-loaded with the core action and immediately followed by the scoping rule. No wasted words, though it is arguably too terse to be fully useful.

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?

A write tool with no output schema and 0% schema coverage leaves the 'key' parameter, the interests format, and the effect on existing data undocumented. For an internal whats_new helper this is tolerable, but an agent still lacks what it needs to call it correctly outside that flow.

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 param burden. 'one entry per project' does hint at the projects array structure, but the optional 'key' parameter and the name/interests sub-fields are entirely unexplained in both schema and description.

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: 'Replace the person's interests', and clarifies the shape with 'one entry per project'. This is clear enough for an agent to understand the operation, though it does not differentiate itself from any named sibling beyond the whats_new reference.

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?

'Only used by whats_new' is an explicit scoping/exclusion statement that tells the agent this is an internal tool, not one to select for general preference writing. It stops short of naming alternative tools for related needs, so it is clear context rather than full when/when-not guidance.

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