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

Annotations already declare destructiveHint=true and idempotentHint=true, so the mutation profile is known. The description adds a genuinely useful side-effect boundary — that the shared city catalog record is never edited — which annotations cannot express and which guards against a plausible catastrophic misunderstanding.

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 waste; the action is front-loaded and the scoping caveat follows. Nothing could be removed 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 5-parameter, 2-required mutation tool with fully documented schema and no output schema, the description plus annotations cover the essentials. It stops short of covering prerequisites, failure modes (e.g. ambiguous city_name), or whether the association's other fields survive the swap.

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 city_id/city_name either-or logic, country disambiguation, and the trip_city_id provenance are all fully documented in the schema. The description adds no parameter meaning beyond that, so the baseline 3 applies.

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: 'Replace one trip-city association with another city.' This is clearly distinguishable from the add/remove/reorder siblings in concept. It does not name those siblings directly, so the agent must infer the boundary from the verb alone.

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 word 'replace' implies this is for changing an existing association rather than creating one, but no when-to-use condition, prerequisite, or alternative (trip_city_add, trip_city_remove) is stated. The agent gets no explicit routing guidance.

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