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

"Only provided fields change" is genuinely useful behavioral information that annotations do not convey, since destructiveHint=true alone does not tell the agent updates are sparse. However, it never explains the destructive aspect (any risk of overwriting/clobbering values) and the stated PUT endpoint conventionally implies full replacement, which sits at odds with the partial-update claim.

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 sentences, zero filler, with the core action and the partial-update constraint front-loaded before the REST routing detail. Nothing could be cut without losing information.

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 four-parameter mutation with full schema coverage, no output schema and a destructiveHint, the description covers the essentials. It stops short of explaining the destructive semantics flagged in annotations, auth requirements, or how to clear an existing field value, and the PUT-vs-sparse-update wording leaves a small ambiguity.

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%, so the schema already documents id, data, name and email; the description adds only the sparse-update semantic for omitted fields. That is the baseline expectation when the schema does the heavy lifting, with no extra syntax or format detail contributed.

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 fields on an existing contact") and qualifies it as targeting an existing record, which implicitly separates it from reamaze_create_contact. It does not name or contrast any sibling explicitly, so it lands just short of full sibling differentiation.

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 by "existing contact" plus the partial-update note, so an agent can infer this is for modifying a known contact rather than creating one. There is no explicit when-to-use/when-not guidance and no mention of prerequisites such as needing the contact id or prior lookup via reamaze_get_contact.

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