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

Annotations already declare the tool read-only, idempotent, and non-destructive, so the description does not need to restate those traits. It adds useful behavioral context by specifying the exact data scope and the provenance of the required identifier, going beyond what annotations provide.

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 one sentence that front-loads the main purpose and includes only relevant details: what is fetched and where the identifier comes from. There is no filler, repetition, or unnecessary elaboration.

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 a single parameter, rich annotations, and an output schema present, the description covers everything needed to invoke the tool correctly. It explains what data the call returns and how to obtain a valid identifier, while the output schema handles return-value details.

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 for the single 'id' parameter is 0%, so the description carries the burden of explaining it. It does this well by defining the parameter as an 'exact day identifier returned by search or list_days', which tells the agent where to obtain a valid value. It stops short of giving an explicit format or examples, but for a single parameter this is sufficient.

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 a specific verb ('Fetch') and a precise resource: published editorial text, dates, primary sources, and correction history for an exact day identifier. It distinguishes itself from siblings by stating the identifier must come from search or list_days, so an agent can tell it apart without inspecting schemas.

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 guidance on when to use the tool: after obtaining an exact day identifier from search or list_days. It does not explicitly list exclusions, such as when to prefer list_topics or list_days, but the input-source constraint is enough to prevent obvious misuse.

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