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

Annotations already cover safety (readOnly, idempotent, non-destructive, open world), and the description adds substantial context they cannot carry: the free-tier quota (5 successful calls per UTC day per network address), which outcomes are uncharged (not_found, fetch_failed), the requirement to send X-API-Key afterwards, and the 0.04 credit cost on success. It also discloses the conditional return behavior for a missing version, which is exactly the kind of behavior an agent needs before calling.

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?

Front-loaded with purpose and outputs, then scoping, then the commercial mechanics; almost every sentence carries operational weight. The signup URL and credit pricing are necessary but make the tail denser than ideal.

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?

There is no output schema, so the description has to describe return values and it does: the four facts plus the latest-stable fallback and version_found. It also covers failure modes (not_found, fetch_failed) and their billing treatment, leaving nothing an agent needs for a correct call 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 coverage is 100%, so the baseline is 3, but the description adds real meaning: 'Send vendor/package' clarifies the expected identifier shape, and it explains the version parameter's effect plus the version_found=false outcome when a release is absent while the latest stable is still returned. That goes beyond the schema's terse 'Optional release to select.'

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 (read) and resource (current Packagist facts for one PHP package) and enumerates exactly what comes back: latest stable version, required PHP, license, abandoned status. It does not explicitly contrast itself with the sibling check_dependency, so it stops short of full sibling differentiation.

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 trigger point ('Use it before composer require') and an explicit scope exclusion ('This does not list vulnerabilities'), which tells the agent when not to reach for it. It never names check_dependency as the alternative for dependency-level questions, so the routing decision between siblings is left to inference.

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