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

Annotations only cover read-only/idempotent/open-world safety, and the description adds real behavioral context beyond them: count is feeds rather than posts, based on a one-in-four sample, prior_count is the previous week's value, data refreshes daily, and an empty array means the rollup lacks two comparable days. It stops short of describing ordering details or maximum result behavior, which keeps it from a 5.

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 first sentence front-loads what the tool returns and the rest is dense, load-bearing qualification about the metric and edge case. The trailing 'Served by RSSAmp (https://rssamp.com/mcp)' line is low-value filler that slightly dilutes an otherwise tight definition.

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 no output schema, the description carries the burden of explaining returns, and it does name count, prior_count, ranking, and the empty-list condition. For a two-parameter read tool with fully documented params, that is close to complete; only ordering/pagination behavior and the interaction between limit and the ranking remain unstated.

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 both limit and window (including defaults and bounds) are already documented in the schema. The description's phrase 'days per side of the comparison' loosely reinforces window but adds no format or interaction detail beyond the schema, so the 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?

The description states a specific verb-like outcome (subjects ranked by increased headline usage over the prior week) and constrains the corpus to English blogs and news sites. It is clear what the tool returns, though it never names the closely related rssamplifier_list_topics / rssamplifier_get_topic siblings, so differentiation is left implicit.

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?

Usage is implied by the metric explanation – you use it when you want movement rather than coverage – and the empty-list case is explained. But there is no explicit 'use this instead of X when Y' guidance or statement of prerequisites, so an agent must infer when this beats listing or fetching a specific topic.

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