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

Goes well beyond the annotations by disclosing what actually changes (leaves New Bookings tab, remains in Inbox, remains searchable), that it cannot be undone with a tool, the per-call confirmation default, the 'reaches other people' caveat, and the required API key scope. This is rich, non-obvious behavioral context on top of readOnlyHint=false and destructiveHint=false.

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?

Front-loaded with the core action and effect, and every sentence carries usable information. Slightly repetitive, as the 'leaves the New Bookings tab' effect is stated twice, but it is well structured overall.

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 one-parameter tool with no output schema, the description covers the effect, reversibility, confirmation behavior, cross-user impact, and auth requirement. Nothing an agent needs to call it safely and correctly 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 description coverage is 100% and the single parameter is fully documented there (origin from search_bookings/list_new_bookings). The description adds no format or syntax detail beyond the schema, 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 concrete verb and resource ('Marks one new booking as read') and precisely describes the state change: the booking leaves the New Bookings tab but stays in Inbox and searchable. This clearly distinguishes it from siblings like list_new_bookings/search_bookings, which surface bookings rather than acknowledge them.

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 clear context ('Hostelworld asks you to do this for every booking') and points to the source of the input ('booking_ref from search_bookings or list_new_bookings'). It does not explicitly contrast against alternatives, but the workflow and confirmation requirement are well established.

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