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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds real value on top: payload size (~15 KB), stability of content across calls, and the project-tagging behavior with its error=project_not_found failure mode. Return format detail is thin, but size plus caching guidance is the more actionable information here.

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 short sentences with zero filler: what it returns, when to call it and how to cache it, then the optional parameter's effect. The most important facts (session-start call, do not re-fetch) are front-loaded.

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 single optional parameter, no output schema, and fully annotated read-only tool, the description covers everything an agent needs: purpose, size, call cadence, caching, and the optional project scoping with its failure case. 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?

Schema description coverage is 100% and the schema already documents the alias/UUID semantics and the project_not_found error. The description adds only the framing that the result is a 'project-tagged copy', which is a minor clarification rather than new meaning, so the baseline of 3 applies.

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?

The description names a specific verb and resource: returns the long-form Skein agent guide in markdown, with an approximate size (~15 KB) that tells the agent what to expect. The resource is distinctive enough that it is unlikely to be confused with siblings like skein_get_monitor_script, but no sibling is named to make the distinction explicit.

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?

It gives concrete timing guidance: call once at session start and cache for the session because the content does not change between calls. That implicitly tells the agent not to re-call, which is strong guidance, though no alternative tool is named for cases where different information is needed.

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