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

Annotations only declare the tool is a non-read-only, non-destructive mutation. The description adds real behavioral context beyond that: cost ($0.05), API key requirement, that source is forced to 'agent', that 'verified' is server-reserved, and that platform=other requires a label. It doesn't describe what happens to conflicting existing rows beyond the primary-unset rule.

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 purpose, then dense parenthetical detail on modes, status, source, and cost. Every clause carries information, though the prose is packed into one block and could be split for scannability.

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 an output schema present the description needn't explain returns, and it covers the operationally important gaps: cost, auth, idempotency-key presence, status semantics, and the upsert-vs-update switch. Minor omission is behavior on duplicate/conflicting rows under the upsert path.

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 coverage is 67%, and the description compensates well, pinning down the status default ('likely'), the 'verified'-is-server-only rule, the source value, and the label requirement for platform=other. It duplicates a few schema-documented behaviors (is_primary, account_id) rather than extending them, keeping it short of a 5.

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 opens with a specific verb+resource ('Upsert a platform account on a Dayze Contact') and enumerates example platforms, so the intent is unambiguous. It never names a sibling like remove_person_account or add_person_alias to route the agent, so it is clear but not sibling-differentiating.

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?

It distinguishes the two operating modes precisely: 'Pass account_id to update a specific row; otherwise upsert by person+platform+handle+kind.' That tells the agent which key path applies. It stops short of stating when this tool is preferable to sibling account/identity tools.

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