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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the incremental value here is the published-only visibility rule, which tells the agent that some valid-looking dates may legitimately return nothing. The return format note adds modest context but does not discuss errors or what happens for unpublished dates.

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 tight sentences, front-loaded with what the tool returns, then the default behavior, then the availability caveat. Minor redundancy between 'Omit date for the latest published edition' and the schema's identical default note.

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, return values needn't be spelled out, and annotations carry the safety profile. The description covers format, default behavior, and the published-only constraint, leaving only minor gaps like error behavior for unpublished dates.

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 both parameters are fully described there (date format/default, lang enum). The description only restates the date default and says nothing about the lang parameter, so it adds little beyond the schema — 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?

States a specific verb+resource: retrieves one edition of the First Light morning brief, and even characterizes the return shape (markdown with key number and numbered snippets with links). It implicitly separates itself from list_first_light ('one edition' vs a list) but never names the sibling, so the differentiation is left to inference.

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?

'Omit date for the latest published edition' gives clear invocation context for the default case, and 'Only editions already released to readers are available' sets a real availability boundary. It stops short of naming alternatives such as list_first_light for browsing editions or get_article for individual items.

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