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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so safety is covered. The description adds genuinely useful return-shape context (changed facts with before/after values and observation location) since no output schema exists, but it leaves the core mechanism opaque: what constitutes 'earlier results', and what happens when no prior results exist.

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?

A single dense sentence with no filler, and the result payload is front-loaded after the verb. Minor ambiguity: 'a list' instead of 'a collection' costs a moment of interpretation but no real bloat appears.

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 single-parameter read tool with annotations and no output schema, the description covers what comes back but omits two things an agent needs: an explanation of the comparison baseline and any indication of the expected identifier form. Adequate but with clear gaps.

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 0% — the only parameter is bare ('Collection Id', minLength 1). The description gestures at it with 'a list' but never connects the term to collection_id, says nothing about accepted identifier formats (ID vs. slug vs. name), and does not compensate for the documentation gap.

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 uses a specific verb and resource ('Compares a list with its earlier results') and enumerates the returned content ('each changed fact, before and after, and where it was seen'), which distinguishes it from get_collection or list_collections. However, it never explicitly names those siblings, so an agent must infer the boundary from wording alone.

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 only implied: the agent can infer this is the tool for inspecting deltas rather than current state, but there is no explicit 'use this when... / use get_collection instead when...' guidance. No prerequisites, no mention of whether a prior snapshot or export is required for a comparison to exist.

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