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

readOnlyHint=true already declares the safety profile, so the description's added value is disclosing the payload: 'full markdown text' tells the agent to expect raw content rather than metadata or a summary, which is not in the annotations or schema. Minor gap on error behavior for nonexistent slugs keeps it from 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 front-loaded sentence with the verb, scope, key, and slug source — no filler, nothing withheld that belongs earlier.

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 one-parameter read tool with annotations covering safety, the description supplies purpose, input provenance, and return format — enough to call it correctly. Only the failure mode for an unknown slug is left 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?

With one parameter at 100% schema coverage the schema already carries the type and example, so the baseline is 3. The description earns above baseline by naming the slug's provenance ('get slugs from list_posts'), which the schema does not explain.

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 and resource ('Read the full markdown text of one blog post') plus the addressing key ('by slug'), and explicitly scopes to a single post, which separates it from the sibling list_posts. An agent can select this over list_posts/search_posts without opening the schema.

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 routes the prerequisite step to list_posts ('get slugs from list_posts'), giving clear usage context. It does not say when to prefer this over search_posts or related_posts, nor what happens with an invalid slug, so no explicit exclusions.

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