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

Annotations already indicate this is not read-only (readOnlyHint=false) and not destructive (destructiveHint=false). The description adds behavioral context: blocks are appended to the end, and each block must follow a specific structure with required fields id, version, type, data along with a list of supported types. It does not cover side effects, permissions, or error conditions, but the annotations provide the safety profile. This is a reasonable addition beyond the annotations.

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 extremely concise at two sentences, with the key action and requirement front-loaded. Every word serves a purpose: the tool's action, target, block format, and supported types. No fluff or repetition.

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?

Given the tool's moderate complexity (2 parameters, detailed nested schema, and an output schema), the description covers the core functionality well. It explains the block requirement and lists all 17 block types. It does not discuss return value (output schema exists), error handling, or edge cases, but for an append tool this is sufficient. The presence of an output schema alleviates the need to describe return values.

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 100%, meaning the schema already fully documents the two parameters (postId and blocks). The description summarizes the block structure and lists types, which adds some convenience but does not clarify parameter semantics beyond the schema. For instance, it doesn't explain how to construct a block's 'data' for each type (though the schema's oneOf provides that). So the description adds marginal value, earning a baseline 3.

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 verb 'Append' and the resource 'blocks to a post'. It specifies that blocks are added to the 'end of a post', which is precise. Sibling tools like 'remove_post_block', 'reorder_post_blocks', and 'replace_post_block' have distinct purposes, so this tool is well-differentiated.

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 implies when to use this tool (to add blocks at the end of a post) but does not explicitly mention when not to use it or provide alternatives. For example, it doesn't contrast with 'replace_post_block' or 'insert' (if such existed). The usage context is clear but lacks explicit exclusions or guidance on adjacent tools.

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