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

Annotations already declare readOnlyHint=false and destructiveHint=false, so the mutation/safety profile is covered structurally. The description's added value is the authorization requirement (write scope), which annotations do not express. It says nothing about whether omitted fields are cleared, whether unknown fields error out (additionalProperties=false), or what the response looks like.

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 short sentences with zero filler, and the operation is front-loaded ahead of the permission requirement. Nothing is redundant, though the brevity edges toward under-specification rather than tightness.

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 9-parameter mutation with no output schema, the description omits the semantically important question of whether this is a partial update or a full replace (only id is required, which strongly implies partial). It also leaves error behavior and the write-scope failure mode unexplained. This is too thin for the complexity of the tool.

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 every one of the nine parameters carries its own description, so the schema does the heavy lifting. The phrase "a contact's details" adds no syntax, formatting, or constraint information beyond that baseline.

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?

"update a contact's details" gives a specific verb (update) and resource (contact), so the operation is unambiguous. It stops short of differentiating from siblings such as create_contact or get_contact, which is what a 5 would require.

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 names a prerequisite ("requires write scope") but gives no when-to-use guidance and no exclusions or alternatives. An agent must infer on its own whether to reach for create_contact, delete_contact, or get_contact in adjacent situations.

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