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 value by enumerating what the response contains (summary, status with evidence, links, contracts on Arc, sources), which matters since there is no output schema. It says nothing about unknown-slug behavior or completeness of coverage, keeping it below 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?

A single dense sentence that front-loads the resource and lookup key, then projects the returned content. No filler, no restatement of the title.

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 and full annotation coverage, the description supplies what an agent needs: what the identifier is, where to get it, and roughly what comes back. It omits edge behavior (invalid/missing slug, whether the record can be stale) but nothing essential to a correct call 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 description coverage is 0% for the single slug parameter, so the description must carry the meaning — and it does, explaining that the slug identifies a project and that valid slugs originate from arc_ecosystem. No format example is given, but the origin guidance is the practically useful detail.

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 resource (one project in the Arc ecosystem directory) and the exact lookup key (slug), which clearly separates it from the list-style siblings (arc_apps, arc_ecosystem, arc_verified). The phrase 'by slug' signals a single-item detail fetch rather than a search or enumeration.

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 precondition for use: slugs come from arc_ecosystem, which tells the agent to obtain valid input from that sibling first. It does not state when NOT to use this tool or contrast it with arc_app/arc_app_history, so it falls short of a full routing guide.

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