lookup_post

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

With no annotations, the description carries the full burden and does well: it discloses the metadata-only behavior, that no media files are written, that it applies to public posts, and that it shares the decode pipeline with extract_post. It omits failure modes (private/deleted posts) and any rate-limit or auth expectations, which 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?

Two sentences, zero filler: the core behavior leads, the routing guidance follows. The dense em-dash clause is still readable and every phrase (field list, --no-download, public) 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?

With no output schema and no annotations, the description compensates by enumerating returned entities (author, caption, timestamps, media URLs, carousel shape) and the file-writing side effect. Remaining gap is error/edge-case behavior for non-public posts, which is minor but real.

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% — url format and out_dir/manifest semantics are already documented in the schema, including share links and bare shortcodes. The description reinforces the manifest output but adds no format or constraint detail beyond the structured fields.

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 ('metadata-only lookup of a public Instagram post') and explicitly positions itself against the sibling extract_post ('same decode pipeline as extract_post but with --no-download'). It even enumerates what metadata is returned, so an agent can distinguish it from extract_post without opening either 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?

It gives a clear selection condition ('Use this when you only need to read the post') and implicitly routes download needs to extract_post via the --no-download contrast. It stops short of an explicit when-not or a named alternative invocation, but the context is unambiguous.

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