One Sparkflights fare by the numeric id from search_deals: its itinerary, the price text of its fare page, its outbound and return flights, the date pairs its fare page lists with their prices, and its url, route_url and feed_url. A fare that is no longer live returns an error naming its route page.
| Name | Required | Description | Default |
|---|---|---|---|
| id | Yes | Deal ID |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the safety profile is covered. The description adds meaningful behavior beyond that: it enumerates the returned data and specifies the error behavior for a stale fare ('returns an error naming its route page').
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 front-loaded with the core purpose and then lists the returned fields compactly. It is a single dense sentence but every clause (source of id, returned fields, error case) earns its place.
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 no output schema, the description carries the burden of explaining returns, and it does so by enumerating itinerary, price text, flights, date pairs, and URLs. The error case for stale fares is also covered, leaving nothing essential for an agent to call this correctly.
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 single parameter is documented as 'Deal ID'. The description adds value by clarifying that the id is numeric and originates from search_deals, which the schema does not state.
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 ('One Sparkflights fare by the numeric id') and explicitly distinguishes it from the sibling search_deals by describing retrieval by id rather than search. An agent can select between the two tools without opening either 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?
The description makes clear the id must come from search_deals, which implies the lookup-after-search workflow, and explains what happens when the fare is no longer live. It lacks an explicit 'use this instead of search_deals when...' statement, but the context is clear.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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