update_contact

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

Annotations cover the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false), and the description adds genuinely useful behavior: only sent fields change, empty string clears text fields, and custom_fields merges per key with null clearing a single value. The one gap is that it does not say what happens when `id` does not exist, which matters for a non-idempotent 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?

Short, front-loaded sentences with no filler; the partial-update rule comes first and the field-level edge cases follow. The opening 'Update a contact' slightly duplicates the title, but the rest of the text is dense with meaning.

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 7-parameter mutation with nested custom_fields and no output schema, the description covers the risky parts well (partial semantics, empty-string clearing, per-key merge). Missing only error/edge behavior for unknown IDs and any note on how the updated contact is returned.

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?

With 71% schema description coverage, the baseline is 3, and the description mostly restates what the schema already says about empty-string clearing and per-key merging. It does add the clearing behavior for `notes`, which is undocumented in the schema, but leaves `stage` and `id` semantics untouched.

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 ('Update a contact') and immediately qualifies the semantics as a partial update. It is clear what the tool does, but it never names or contrasts with the close sibling `upsert_contact`, so an agent must infer which one to pick.

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 implies usage through its partial-update framing (use when you want to change only some fields), but it gives no explicit when-to-use/when-not guidance and does not route to `upsert_contact` for create-or-update cases. Usage has to be inferred.

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