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

The description discloses useful facts like 'Max 20 entries, max 100KB per entry. Oldest entries are removed when limit is reached.' However, the annotations declare readOnlyHint=true and idempotentHint=true, which directly contradict the described 'Add an entry' operation—a write that creates a new entry each time and is not idempotent. This is an annotation contradiction.

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 awkwardly structured with nested parentheses and repeats 'personal journal'. The core information is present, but unnecessary repetition and punctuation hinder readability. It could be condensed into a cleaner single sentence.

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?

The tool is simple, but the annotation contradiction and inconsistent size limits create conflicting expectations. It does cover purpose and retention, but missing behavioral consistency and valid input ranges make it incomplete for reliable agent use.

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%, so baseline is 3. However, the description introduces a conflicting size limit: 'max 100KB per entry' while the schema's entry maxLength is 30000 bytes. This can mislead an agent about valid input. The description adds no useful parameter-level semantics beyond the schema.

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 specific action 'Add an entry to your captain's log' and distinguishes it from sibling tools like captains_log_delete, captains_log_get, and captains_log_list by using the verb 'Add'. It also elaborates on the journal's purpose, making the tool's function unmistakable.

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 explicit context with 'Use this to record discoveries, plans, contacts, and thoughts,' and the overall purpose of a personal journal. It does not explicitly mention alternatives or when not to use, but the sibling set makes this the obvious write operation, so clear context is present.

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