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

Annotations already declare destructiveHint=true and readOnlyHint=false, and the description reinforces this with 'replaces the stored value', telling the agent that the previous title/company is overwritten rather than merged. It does not cover auth requirements, failure modes, or the dry_run preview path beyond what the schema states, so it is useful but not comprehensive.

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?

Four short sentences, front-loaded with what it does, then when to use it, then overwrite behavior, then the minimum-input rule. No filler; slight redundancy between 'Update an existing contact's job title and/or company' and 'a new title or employer' is the only waste.

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 6-param mutation with no output schema, the description covers purpose, trigger, overwrite semantics, and the minimum required input, leaving the person/project/dry_run mechanics to a fully documented schema. It could say more about what a successful update returns or whether partial updates preserve untouched fields, but the essentials for correct invocation are present.

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 100%, so baseline is 3, but the description adds a real constraint absent from the schema: 'Give at least one of title or company', which the JSON schema does not enforce (only contactId is required). That single sentence prevents a no-op call and earns above 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?

States a specific verb and resource ('Update an existing contact's job title and/or company') and adds scope ('on this member's own contacts'). It explicitly separates itself from creation-oriented siblings with 'does not create contacts', so an agent can distinguish it from connections_contacts_save_contact without opening either schema.

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?

Gives a clear triggering condition: call it when the member supplies a new title or employer for someone already in their contacts. It excludes the create case but never names a sibling alternative (e.g. save_contact, connections_contacts_get) explicitly, so routing is inferred rather than spelled out.

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