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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds real value beyond that: the data source file, the null-preservation rule for unknown values, the note that results include each provider's availability checker and source links, and the caveat that ranges are not address-specific. Pagination behavior is unmentioned.

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?

Three sentences, each front-loaded with the most decision-relevant content: what it compares, how to filter/sort, and what the results and caveats are. No filler or repetition of schema enums verbatim.

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 helpfully states what each result contains (availability checker, source links) and the null/verification caveats. It is nearly complete for a read-only query tool, but omits pagination semantics and default sort behavior, which an agent needs to page results correctly.

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 only 10%, so the description must carry the load. It does map most filters semantically (country, technology, advertised speed, listed monthly price, commitment duration, provider) and explains sort keys including 'indicative price per advertised Mbps'. However, limit/offset pagination is never mentioned, units for price and speed are not clarified, and the schema's odd 'country required but documented as optional' tension is left unaddressed.

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 ('Compare provider-level home internet summaries') and names its data source, immediately distinguishing it from siblings like compare_mobile, compare_energy, and compare_digital. An agent can identify the tool's scope 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?

The description gives clear usage context: filter/sort dimensions and the crucial exclusion that this source holds summarized ranges, not individual address quotes, so availability must be confirmed with the provider. It stops short of naming alternative sibling tools or explicitly stating when not to use it versus, say, compare_mobile.

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