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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds genuinely non-derivable behavior: these journeys stay counted in presence calculations and gaps until resolved, which explains why the read matters. It stops short of describing ordering, paging, or volume of returned items.

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?

Three sentences, each doing distinct work: trigger, return payload + side effect, then the follow-up action policy. Front-loaded with the trigger. Slightly dense with workflow instruction, but no sentence is redundant.

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?

With an output schema present, the description does not need to enumerate return fields, yet it still characterizes them (awaiting-confirmation journeys + preference flag). Combined with zero parameters and full annotation coverage, an agent has everything needed to call it correctly and act on the result.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline for an empty schema is 4. The description correctly avoids inventing inputs and instead spends its words on workflow.

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 (returns) and specific resources (past booked journeys awaiting confirmation plus the owner's automatic-completion preference), which clearly separates it from list_journeys and get_journey. The phrase 'Call on entry to the ledger' also frames it as a review/queue tool rather than a generic fetch.

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 invocation trigger ('Call on entry to the ledger') and names the downstream alternative with its precondition: 'use update_journey with status completed only after confirmation, or correct/delete changed travel.' That is when-to-use plus what-to-do-next plus named siblings, not inference.

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