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

It discloses substantial behavior beyond the annotations: Auto-Merge may add values to an existing contact, each 200/201 outcome is explained, possible duplicates enter review, and the storage account and subsequent sync behavior are specified. It also explains that over-limit contacts are retained frozen without syncing and recommends an idempotency key for safe retries, exposing important side effects and operational consequences.

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?

The description front-loads the core action and possible outcomes, using bullets effectively for the merge/create branches. The following short paragraphs each cover a distinct, consequential behavior, and the final retry sentence is concise; there is no filler despite the density.

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?

Combined with the fully documented nested schema, the description supplies enough context to invoke a complex create operation correctly, and its status outcomes are especially useful because there is no output schema. Minor gaps remain around explicit sibling routing, what happens when no eligible two-way account exists, and the response payload beyond the named statuses and `contact.frozen`.

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 schema already thoroughly documents the body fields, update/clearing semantics, and idempotency-key behavior. The description's recommendation to send `Idempotency-Key` on retries is useful operational emphasis but largely repeats the schema; most other description text concerns operation-level behavior rather than additional parameter meaning.

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 opening "Adds a contact" states a clear verb and resource, while the `merged`, `created`, and `needs_review` outcomes clarify that the operation does not always produce a new record. It does not explicitly distinguish this tool from the sibling `contact_change`, so sibling differentiation remains incomplete.

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?

The description provides practical context for creation, automatic merging, duplicate review, account selection, plan-limit handling, and safe retries. It does not state when not to use the tool or direct updates to `contact_change` and lookups to `contact_find`, but the intended creation context is otherwise clear.

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