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

With no annotations, the description carries the full burden and does disclose the return payload: hydrated post fields (author, counts, media, tags, provenance, embedded repost/quote target, text up to 262144 characters) plus the parent post. It does not describe failure behavior for a bad txid or any auth/rate-limit context, so it falls short of fully transparent.

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 compact sentences with zero filler. The purpose is front-loaded, the return contract second, and the sibling routing last.

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?

With no output schema the description appropriately spends its words on the return shape, and it names the parent/self relationship, which an agent needs to interpret the result. Only error and edge-case behavior (unknown txid, missing parent) is unaddressed.

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?

There is one parameter with 100% schema description coverage, so the schema already documents txid. The description only echoes the lookup key ('by txid') and adds no format or validation detail; the 262144-character figure refers to returned text, not the parameter. Baseline 3 is correct.

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+resource+lookup key: 'Get full details of a single post by txid.' The scope ('single post', not its replies) and the exact response shape {post, parent} are stated, which cleanly separates it from peck_thread and peck_user_posts.

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 agent away from this tool for reply retrieval: 'Use peck_thread for the replies.' That names the alternative and the condition selecting it, leaving no inference required.

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