substack_add_image

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

With no annotations provided, the description carries full burden for behavioral disclosure. While 'Add' implies a mutation operation, it doesn't specify whether this requires authentication, what happens on failure (e.g., invalid URL), whether images are embedded or linked, or if there are rate limits. For a write operation with zero annotation coverage, this leaves significant behavioral gaps unaddressed.

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 a single, focused sentence that wastes no words. It front-loads the core action ('Add an image') and target ('to a draft') efficiently. Every word earns its place, making it immediately scannable and understandable without unnecessary elaboration.

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 mutation tool with 4 parameters, no annotations, and no output schema, the description is insufficient. It doesn't cover what the tool returns (success/failure, image ID), error conditions, or how it interacts with draft state. Given the complexity of adding media to a publishing system, more context about behavioral outcomes is needed for the agent to use this effectively.

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 75% (3 of 4 parameters have descriptions), providing good baseline documentation. The description adds no parameter-specific information beyond what's in the schema—it doesn't explain draft_id context, URL format requirements, or caption/alt usage. Since the schema does most of the work, the baseline score of 3 is appropriate despite the description's lack of parameter details.

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 ('Add') and target resource ('an image to a draft'), making the purpose immediately understandable. It distinguishes this from sibling tools like 'substack_append_to_draft' or 'substack_update_draft' by focusing specifically on image addition. However, it doesn't specify whether this adds images to existing content or creates new sections, leaving some ambiguity compared to more detailed alternatives.

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?

The description provides no guidance on when to use this tool versus alternatives like 'substack_append_to_draft' (which might handle general content) or 'substack_update_draft' (which might modify existing elements). There's no mention of prerequisites (e.g., needing an existing draft), constraints, or typical use cases, leaving the agent to infer usage from the tool name alone.

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