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

Annotations already cover the safety profile (readOnlyHint=true, idempotentHint=true, destructiveHint=false, openWorldHint=false), so the description rightly does not repeat it. It adds genuine extra context: the cost behavior ('FREE — this call costs nothing') and the scope constraint that ids are account-specific and cannot be guessed. No contradiction with annotations.

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 earning its place: purpose+output, usage-ordering rule, and cost note. The core purpose is front-loaded in the first sentence. The 'FREE' note is a minor addition but is genuinely useful behavioral information rather than padding.

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 parameterless list tool with a full output schema and safety annotations, the description covers everything an agent needs: what is returned, that it must be called first, that ids come from here, and that it costs nothing. Nothing material 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?

The tool has zero parameters, so the baseline is 4 and there is nothing to document beyond it. The description does mention the output fields (id, name, slug, custom domain, page count), which adds value for interpreting the result even though it is arguably output-schema territory.

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 ('Lists') and resource ('every programmatic-SEO project this API key can act on'), plus enumerates the returned fields (id, name, slug, custom domain, page count). The scope qualifier 'can act on' and the collection semantics clearly distinguish it from seo_project_get (single project) and seo_project_create (creation) among siblings.

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?

Provides explicit, imperative routing: 'Call this FIRST in any session — every other tool needs a projectId from here.' It also states the negative case — ids cannot be guessed or carried over from another account — which tells the agent why this tool is mandatory rather than optional. This is exemplary usage guidance.

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