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

Beyond the readOnlyHint/destructiveHint annotations, the description adds genuinely non-obvious behavioral traits: 'never triggers a live run' and 'preserves the last good result after a newer failure,' plus the 'independently verified' nature of the retained result. These traits materially change what an agent should expect from a data-retrieval call, and nothing contradicts the annotations.

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 with no wasted words: sentence one states the purpose and both modes, sentence two adds the behavioral caveats, sentence three routes the user to the portal with a URL. Every sentence earns its place and the core purpose is front-loaded.

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 two-parameter read-only tool with full schema coverage and safety annotations, the description covers purpose, behavioral expectations, and out-of-scope actions well. The only gap is that with no output schema, the exact return shape and empty-result/before-timestamp-no-match behavior are not specified, though the 'preserves the last good result' hint mitigates this.

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%, so the schema already fully documents both dataFeed and capturedAtOrBefore, including the ListWebDataFeeds reference and the ISO-8601 semantics. The tool description adds context about the overall behavior but no parameter-level detail beyond the schema, so the baseline of 3 is appropriate.

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 a specific verb and resource: 'Get the latest independently verified stored result for one of the caller's web data feeds,' and covers both retrieval modes (latest, or latest at/before a timestamp). It distinguishes itself from the many sibling Get* tools by scoping to the caller's own stored feed results and explicitly noting it never triggers a live run.

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 gives clear context on when to use the tool — when a stored, verified result is wanted rather than a live computation — and explicitly routes create/manage workflows away from it ('To create or manage a feed, tell the user to open the Equibles Portal'). It does not explicitly name a sibling alternative for listing feeds (though the schema's dataFeed parameter does point to ListWebDataFeeds), so a fully explicit exclusion is slightly lacking.

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