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

Annotations already declare readOnlyHint=true and the description is consistent with that (nothing suggests mutation). It adds cost/latency context ('Free and instant') and explains what the card contains (venues by kind, groceries, nearest stop, map facts), which is genuine value beyond the annotation.

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?

Purpose and the key usage trigger are front-loaded, but the tail half is promotional filler — the ground-method URL and the no-account vote page — that doesn't help an agent invoke this tool correctly and dilutes the signal.

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 describing returns; it gestures at contents ('finished picks with receipts', 'running status', block facts) but never characterizes the shape or what 'receipts' actually are. Adequate to call, but an agent still can't anticipate the response structure.

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?

searchId is well covered by the schema description and the description reinforces its provenance ('the searchId from search_stays, or the id in a stayotter.com/stay/s_… link'). However, travellerCountry appears in neither the schema description nor the prose, leaving half of the 50%-coverage parameter set undocumented.

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 states the resource ('the card for a search by searchId') and its two return modes ('finished picks with receipts, or its running status'), which lets an agent distinguish it from search_stays. The verb is implied by a noun phrase rather than stated outright, keeping it just short of a 5.

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?

It names the exact sibling and the condition that selects it: 'Use it to finish a search_stays call that returned running,' plus the secondary case of reading a shared stay link. No inference is required to know when to reach for this tool over search_stays.

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