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

Annotations already declare a safe read (readOnlyHint=true, destructiveHint=false, openWorldHint=false), and the description adds genuinely new behavior: the timeline is capped at the 5 newest events, and an unknown or deleted ID yields {error: "Contact not found"}. It does not discuss auth or permissions, but for a read-only single-record fetch that is a minor gap.

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 purpose and the alternative are front-loaded, and the field enumeration earns its length by telling the agent what it will receive. The parenthetical naming of "Skip AI (bypassReceptionist)" is slightly cluttered but still informative.

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?

There is no output schema, so the description carries the burden of describing returns — it lists the returned fields, the timeline cap, and the not-found error shape. Combined with the usage routing to get_contact_timeline, nothing an agent needs to call and interpret this tool is missing.

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% and the contactId description already says to obtain the UUID from search and that it is not a phone number. The description's "(scope contacts, by name or phone)" restates that guidance rather than adding meaning, so it sits at the baseline for a fully documented single parameter.

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 ("Get one contact by ID") and immediately enumerates the record contents, so the agent knows exactly what comes back. It also distinguishes itself from the two nearest siblings, search and get_contact_timeline, without needing to open 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 an explicit precondition ("use it after search (scope contacts, by name or phone)") and an explicit alternative for the richer case ("for more history use get_contact_timeline"). Both the when and the when-not are named.

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