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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely useful context — the resource is public (no auth implied) and 'Costs 1 credit' discloses a metering constraint — but it does not describe caching behavior, error cases, or pagination.

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?

Two tight sentences that front-load purpose and follow with payload and cost. The bare 'Post.' opener is slightly redundant with the title but the remaining text earns its place.

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 simple 2-param read tool this covers purpose, returned content, and cost. With no output schema, the return description is helpful, but the undocumented cache_max_age parameter leaves a gap an agent would need for correct invocation.

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 only 50%: 'url' is documented in the schema but 'cache_max_age' is undocumented in both schema and description. The description adds no parameter meaning, so it fails to compensate for the uncovered optional parameter.

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 and payload: 'A single public Bluesky post with like, reply, repost and quote counts, plus any attached images or video.' The word 'single' distinguishes it in scope from list-oriented siblings like bluesky_userPosts, but no sibling is named explicitly.

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?

There is no when-to-use/when-not guidance and no named alternative. The 'single post' phrasing implies this is for one post rather than a feed, but the agent must infer that bluesky_userPosts or bluesky_profile are the alternatives for listing.

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