Report · marked 25 Aug 2026
mozilla/pdf.js
Solid foundations, held back in a few specific places.
JavaScript · 53,780 stars · 2,549 files · branch master
72
/100
B+
Instructions
23/27Whether the repo tells an agent how to behave before it starts guessing. Losing marks on instruction quality.Setup
8/14Whether an agent can install the project and get it running without a human. Losing marks on discoverable commands.Verification loop
18/25Whether an agent can check its own work. This is the category that most decides whether agent output is trustworthy. Losing marks on test command is discoverable.Context economy
11/20Whether the repo fits in a context window, or fights it. Losing marks on file sizes fit in context and repository weight.Navigability
9/10How quickly anything new can orient itself. Losing marks on repository description.
Higher is better. Accent marks what is costing you most.
Fix these first
01
Test command is discoverable
Add a `test` script or a `test` target that runs the whole suite with no arguments. The convention is the interface — an agent tries `npm test` and `make test` before it tries reading your CI config.
02
Discoverable commands
Declare the handful of commands that matter in package.json scripts, a Makefile, or a justfile. Naming them turns guesswork into a lookup.
03
File sizes fit in context
A single file that fills the context window forces an agent to work from fragments, and it will confidently edit code it never saw. Splitting the worst offenders pays for itself immediately.
The full marking
Every deduction below names the file or setting it came from.
Instructions 23/27 A
Whether the repo tells an agent how to behave before it starts guessing.
✓Agent instruction file
12/12
AGENTS.md is present, which is the format the most tools read.
Also found: CLAUDE.md
✗Instruction quality
8/12
Real instructions, with gaps.
Worth fixing: it never states a build, test, or run command.
7,075 characters, a workable length
uses headings, so an agent can skim it
includes copyable code blocks
✓README as an entry point
3/3
README has a clear getting-started section.
Setup 8/14 B-
Whether an agent can install the project and get it running without a human.
✓Deterministic install
6/6
package-lock.json pins the dependency tree.
Found package-lock.json
✗Discoverable commands
0/6
No declared commands. An agent has to infer how to build and run this from the file tree.
Declare the handful of commands that matter in package.json scripts, a Makefile, or a justfile. Naming them turns guesswork into a lookup.
–Environment config
n/a
Not applicable — this reads as a library, with no environment to configure.
✓Pinned runtime version
2/2
The language runtime version is pinned.
package.json engines.node >=22.13.0 || >=24
–Reproducible environment
n/a
Not applicable — a library doesn't need a container to be worked on.
Verification loop 18/25 B+
Whether an agent can check its own work. This is the category that most decides whether agent output is trustworthy.
✓Tests exist
8/8
1592 test files against 519 source files.
e.g. src/core/file_spec.js, test/.gitignore, test/add_test.mjs
✗Test command is discoverable
0/7
There's no obvious way to run the tests. Even if tests exist, an agent won't reliably find the entry point.
Add a `test` script or a `test` target that runs the whole suite with no arguments. The convention is the interface — an agent tries `npm test` and `make test` before it tries reading your CI config.
✓Continuous integration
4/4
15 GitHub Actions workflows define what "passing" means.
✓Lint and format rules
3/3
eslint.config.mjs encodes the house style.
✓Static type checking
3/3
Strict type checking is on, which catches a whole class of agent mistakes before they run.
Context economy 11/20 B-
Whether the repo fits in a context window, or fights it.
✓No committed build output
6/6
No generated directories committed.
✓.gitignore hygiene
3/3
.gitignore covers 10 patterns.
✗File sizes fit in context
0/6
16 source files are over 100KB.
A single file that fills the context window forces an agent to work from fragments, and it will confidently edit code it never saw. Splitting the worst offenders pays for itself immediately.
external/openjpeg/openjpeg_nowasm_fallback.js — 441KB
test/unit/api_spec.js — 326KB
test/unit/annotation_spec.js — 214KB
✗Repository weight
2/5
About 195MB checked out. Large enough that cloning and searching are both slow.
Large binaries and vendored trees slow every operation an agent performs. Git LFS or a separate assets repo keeps the working tree navigable.
Here is your AGENTS.md
Drafted from what is actually in this repository: the install
command from your lockfile, the commands you already declare, your real directory layout. Anything
marked TODO needs a person. Save it at the root as AGENTS.md.
# AGENTS.md PDF Reader in JavaScript ## Setup ``` npm ci ``` ## Commands ``` # TODO: nothing declares a build or test command, so an agent has to guess. # This is the single most valuable section of this file. Fill it in. ``` ## Layout - `src/` 212 source files - `test/` 126 source files - `web/` 84 source files - `external/` 75 source files - `examples/` 10 source files - `extensions/` 9 source files ## Conventions - Tests live alongside the code they cover, following `src/core/file_spec.js`. - TypeScript runs in strict mode. Type errors are the fastest feedback available, so do not weaken it. - CI defines what passing means. See `.github/workflows/ci.yml`, and keep it green. - TODO: add the two or three conventions a newcomer always gets wrong here. ## Gotchas - `external/openjpeg/openjpeg_nowasm_fallback.js` is 441KB. It will not fit comfortably in context, so read it in parts. --- Drafted by agentreadme.com from what is in this repository. Everything marked TODO needs a human. Check it in as AGENTS.md at the root.
Open the raw markdown
or
curl -o AGENTS.md agentreadme.com/draft/mozilla/pdf.js.md
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Think this mark is wrong?
Every deduction above names the file it came from, so this can be settled by looking. If a check missed something, that is a rule worth fixing.