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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds real value beyond them: result ordering (newest first), the returned fields, the source (endoflife.date, community-maintained), a caveat that it reports published dates rather than whether an install is patched, and a 1-credit cost. It does not explain edge behavior (unknown product slug, empty results), keeping it at 4.

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 purpose is front-loaded as a question, followed by scope, returned fields, usage context, source caveat, and cost — a sensible priority order. The phrasing is tight, though the parenthetical cost note and source sentence add some length that could be trimmed without loss.

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 simple two-parameter read-only lookup with full schema coverage and no output schema, the description adequately covers purpose, ordering, returned fields, source reliability and limits. What is missing is minor: handling of an unrecognized product slug and how truncation by `limit` behaves beyond the schema note.

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% — both `product` (slug examples like php, python, nodejs) and `limit` (integer, 1-100, default 25) are fully documented in the schema. The description only reinforces the ordering semantics ("newest first") already stated for `limit`. Baseline 3 applies since the schema carries the parameter burden.

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 opening question ("Which versions of a product are already end of life?") plus the explicit scope ("Lists the release cycles past their end-of-life date") gives a specific verb+resource. It implicitly separates itself from eol_latest_release by focusing on past-EOL cycles, but never names that sibling, so an agent must infer the routing.

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?

It states a concrete usage context: "Useful for security audits and spotting outdated versions in an estate." That is clear guidance on when to reach for it. There are no exclusions or explicit pointers to alternatives (eol_latest_release, eol_product_search), so it falls short of the 5 bar.

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