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

The description explicitly discloses a destructive operation ('deleteAddressId to remove one'), while the annotations declare destructiveHint=false. This is an annotation contradiction: an agent relying on the hint would underestimate the tool's destructive potential. The description does add a useful combinability note, but the contradiction forces a low score.

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 description is two sentences and every clause carries information; the first sentence gives the general purpose and the second routes to the correct parameter names. It is slightly dense with comma-separated operations, but not padded.

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 tool with six parameters and nested objects, the description covers the address operation modes and combinability. However, it leaves important invocation semantics implicit: whether metadata overwrites wholesale or merges, what happens when an addressId is invalid, and whether all changes apply atomically. The existence of an output schema and full parameter descriptions helps, but an agent still lacks enough guidance for a safe complex update.

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 descriptions already cover all six parameters (100%), so the baseline is 3. The description adds meaningful relationship semantics: add/update/delete are distinct operations and multiple can be combined in one call, which the schema alone does not convey. It does not clarify metadata replacement versus merge, but that gap is not the description's core burden.

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?

The description names a specific verb ('Update') and resource ('agent'), and enumerates the exact modifiable surfaces: name, metadata, and addresses. This clearly distinguishes agent_update from siblings like agent_create, agent_get, and agent_delete without needing to inspect the 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?

It clearly establishes the use case: updating an existing agent and its addresses. It also explains the three address operations and that they can be combined. However, it does not explicitly state when-not-to-use or name alternatives such as agent_create for new agents, so it stops short of a 5.

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