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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful context beyond that: the timestamps are UTC and cover two distinct pipelines (feed download/process vs image gathering) rather than a single 'last updated' value. With no output schema present, it still leaves the exact field names and shape unstated.

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?

Two compact elements, information front-loaded with the endpoint appended for orientation. No filler sentences. The stacked 'when ... and when ...' construction is slightly dense on first read but remains parseable.

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 low-complexity, two-parameter read tool with fully documented schema and non-destructive annotations, the description covers the essential unknown: what freshness data is returned and in which timezone. Only the precise response field names are left implicit, which is a minor gap since no output schema exists.

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%: idx_id names the IDX MLS id format and points to idx_list_approved_mls, and fields explains the rf projection including ["*"] and the size-saving rationale. The description adds nothing about either parameter, 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?

The description names the resource precisely: an MLS feed's last download/process time and its images' last-gathered time, in UTC, scoped to /mls/age/{idxID}. It is clearly a read of freshness metadata rather than listings or MLS enumeration, so it is distinguishable from siblings such as idx_list_approved_mls. The phrasing is a noun clause rather than a verb+resource, which keeps it just below 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?

There is no statement of when to call this versus alternatives (e.g. before relying on cached listing data, or after triggering a feed). No prerequisites, no exclusions, no sibling routing are given. The agent must infer usage entirely from the name and return description.

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