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

Annotations only declare readOnlyHint=true, but the description adds substantial context the agent could not infer: no authentication required, status is recomputed on every call from today's date, upstream data from endoflife.date refreshes every 12 hours, and the result shape changes with the argument combination. The freshness/staleness caveat is exactly the kind of behavioral disclosure annotations cannot carry.

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?

Front-loaded with purpose, then coverage breadth, behavioral semantics, freshness, and usage — a logical order with no filler sentences. It is on the long side for a two-parameter tool, and the product enumeration list of ~18 example names could be trimmed, since the schema already gives aliases and the no-arg call lists identifiers.

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?

No output schema exists, so the description carries the full burden of explaining return values — and it does, enumerating the four status values, release/active-support/EOL dates, days remaining or elapsed, and supported cycles. Combined with the authentication, freshness, and routing details, nothing an agent needs to invoke it correctly is missing.

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%, so per-parameter formats and aliases are already documented, but the description adds combinatorial semantics the schema does not express: product+version returns that cycle's status, product alone returns every release cycle, and neither argument lists all product identifiers. That mapping is genuinely useful, though it restates some schema content.

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?

Opens with a precise verb+resource ('Tells whether a language, runtime, framework, database or operating-system version is still supported') and scopes the domain to ~480 named products. It explicitly carves out its boundary against the sibling package_status ('for a library's own versions use package_status'), so an agent can route correctly without opening either schema.

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?

Gives concrete triggering scenarios — before choosing a runtime or base image, writing a Dockerfile or CI matrix, auditing an old version — and names the alternative tool (package_status) for the adjacent library-version use case. Both when-to-use and when-to-use-something-else are stated, not inferred.

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