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

Annotations already establish that this is a mutation (readOnlyHint=false) and non-destructive. The description adds that only already-marked places are attachable, but it does not disclose whether repeated calls append or overwrite, or how invalid ids are handled. This is acceptable for a simple association operation but not richly transparent.

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 a single, front-loaded sentence that states the action and the only necessary input-source guidance. Every part earns its place and there is no redundancy.

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 simple two-parameter mutation with complete schema descriptions and no output schema, the description plus schema gives an agent enough to call the tool correctly. It could mention response or error behavior, but that is not essential for this operation.

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 schema already provides good descriptions for both parameters, including an example and a note that countries and regions are not attachable. The description adds a useful workflow pointer by directing the agent to list_visited for visit ids, going slightly beyond the schema.

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 uses a specific verb, 'attach', and clearly states the object ('places you have already marked') and target ('a trip'). It also points to list_visited as the source of visit ids, which distinguishes this from sibling tools like add_place, add_country, and add_region.

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 explicitly states the prerequisite: places must already be marked, and visit ids must come from list_visited. It does not explicitly name alternatives or exclusions, but the workflow guidance is clear enough for an agent to know when this tool applies.

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