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

Annotations already cover readOnly/destructive, and the description reinforces with 'Reads or computes only and changes nothing'. It adds genuinely new context the annotations cannot carry: per-call pricing, first-25-free, failed calls free, and an explanation of why repeats are not free (matching idempotentHint=false as a billing rather than a semantic property). The openWorldHint is not addressed.

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?

Purpose, output, usage and example are front-loaded in the first two sentences, and the example is compact. The billing clause is slightly redundant ('first 25 free; failed calls free' followed by 'each call is charged, so repeats are not free'), which costs a little density but not comprehension.

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 only two string parameters, full schema coverage and no output schema, the description carries the necessary burden by describing exactly what comes back (comparison result plus next major/minor/patch) and how pre-releases are treated. Nothing an agent needs to call 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 the baseline is 3, but the description adds real meaning: the example values demonstrate that comparison is numeric-segment based (1.10.0 vs 1.9.3), and pre-release handling such as 2.0.0-rc.1 is called out explicitly. That is more than the schema's bare 'First version'/'Second version' labels.

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?

States a specific verb and resource ('Semver compare of two semantic versions') and spells out the full return: which is newer plus the next major, minor and patch of the first. No sibling tool does version comparison, and the description makes the output shape unmistakable without opening the 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 a concrete decision context ('Use to decide whether an upgrade is a major change') plus a worked example (a=1.10.0, b=1.9.3) that anchors the ordering semantics. It does not name a when-not condition or alternative, though no sibling tool overlaps this function.

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