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

Beyond the annotations (readOnlyHint, idempotentHint, destructiveHint false), the description adds useful context: 'Reads only; nothing is created or modified.' It also discloses the API key requirement for unpublished articles, states what is returned (article object with content_markdown populated), and defines error conditions (slug not found or account cannot see it). This supplements the annotation metadata effectively.

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?

The description is compact yet comprehensive: it opens with the purpose, then gives usage guidance and invokes the listing tools, and finally covers reads-only nature, auth nuance, return format, and error handling. Every sentence adds value, and it is front-loaded with the primary action. No fluff or repetition.

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 tool with one parameter, rich annotations, and no output schema, the description covers everything needed: what it returns (article object with content_markdown populated), auth requirements (API key for unpublished), and failure modes (non-existent slug or permission issue). The complexity is low, and the description is sufficiently complete to guide correct usage.

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% because the only parameter 'slug' is thoroughly described in the schema (e.g., not numeric id, not full URL, with an example). The tool description does not add extra parameter semantics beyond restating 'by slug' in the purpose. Baseline 3 is appropriate because the schema already carries the semantic load, and the description doesn't compensate further (nor need to).

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 clearly states the action ('Fetch a single article by slug') and the resource/scope ('full Markdown body'). It distinguishes itself from sibling tools like list_my_articles and search_articles, which are about listing/searching, while this fetches a specific article.

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?

Explicitly tells the agent when to use it: after list_my_articles or search_articles has provided a slug, and the actual content is needed. It also explains the deliberate trade-off (listing tools omit bodies for cheapness) and gives use cases (reading, editing, repurposing). This is strong usage guidance with clear sequencing and context.

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